What can be the reason for left-sided headache?

Hi doctor,

I have had a left-sided unilateral headache for the last four weeks. The pain varies in place, but it is always centered on my left temporal area. Pain can be on the top of my head, cheek, side of jaw and even chin at times. I have also had momentary ear pain, which is a brief one second flash perhaps inner ear pain for the last week. I went to my doctor after the first week of non-stop pain. Ironically the pain had eased that day and I was left with a sense of pressure in my temple area. It was disrupting my sleep. My heart rate was a bit high. He took an ECG there and he was not sure why I had the headache, so sent me to other hospital. He also looked into my eyes and thought I may have a blurred left optical disc. I had another ECG at the hospital and my pulse rate was still high, sinus tachycardia. But, the nurse told me that everything else with my heart was reading fine. The treating doctor ran through the usual questions and gave a neurological exam. I passed everything from looking into my eyes with a light to reflex tests and making me push him away with my arms and legs and opening my eyes while he pressed gently on them with his fingers. He also ran blood tests and they came back normal. He was not sure what the problem was and was not convinced that my left optical disc was blurred. As it was 1 AM he suggested me to stay overnight, so that I could see a consultant or specialist first thing in the morning. I had my blood pressure taken once again at around 4 AM and the nurse said it was still a little high, but everything was fine. The next morning consultant or specialist saw me for about a minute. He did not even acknowledge my heart rate, just said that as I was feeling totally normal and had no other symptoms other than the pain it was likely a benign tension headache. I was better off at home rather than stuck in hospital. Based on what the treating doctor said he too was not convinced that I had a blurred left optical disc, but wanted me to see an eye doctor at the hospital. I had an eye examination and everything was fine, other than the fact that I need glasses, which I already knew. No issues were detected and my left optical disc was fine. I was then discharged and went home. I asked a nurse about my sinus tachycardia just before I left hospital and she said that the heart does that sometimes and being in hospital or going to the doctor does not help as I was well and healthy. The first thing I did when I got home was checked my heart rate monitor app that I have on my phone. It uses the torch on my phone to detect color changes in one finger to measure beats per minute. I have read that it is very accurate. My resting heart rate at this time was around 75 bpm. I was relieved and put my heart rate down to the anxiety of going to see my doctor about the persistent headache and then having to unexpectedly go to hospital. In the three weeks since my hospital visit I have still got the headache. The pain is in the same place around left temple area, side of jaw, cheek, top of head. The pain is not severe, but annoying. Lying down to sleep at night is what seems to make the pain worse, even after a pain-free day. The pain would flare up as soon as my head hit the pillow, including at the back of my head and yet when staying with my girlfriend I would not get this when sleeping on her pillow. I decided to see my doctor again yesterday after having a sleepless night. I had 48 hours mostly pain-free and occasional pangs of pain. I slept at home fine, then the next night at my girlfriend's fine and then the next night the moment I went to sleep the pain came on and I could not sleep all night. Painkillers would not help. I was also experiencing a kind of dizziness, unless it is all in my head. Nothing spinning or dramatic, but just sometimes felt a bit odd briefly when moving, only when moving. Balance is fine. I had felt this the day after returning from hospital, but it was gone within 24 hours, so I have been free of it for two weeks. I saw a doctor again. He did not have a specific diagnosis, but backed up the idea that it was a benign headache. I have not been stressed or having personal problems as such, so he ruled out anything there. He said pain at the back of the head when laying down can be quite serious, but could not understand why I get that pain at home but not at my girlfriend's house, so said it could not be serious in that case. I was asked to rate that pain out of ten when I get it in bed, I said it can be about 6/10. He asked about a history of migraines which I do not have. Asked if I had any other symptoms which I did not. He checked my oxygen levels and blood pressure. He said my BP was shooting, but I said it was anxiety because two weeks prior it had returned to normal as soon as I got home from hospital, so I thought it was likely high because I was anxious of being at the doctors. He prescribed me 2 x 28 tablet boxes of Naproxen 500 mg twice a day and asked me to let him know how I was getting on with it after five days. He also checked my jaw, pushed down on my shoulders, etc., and all was fine. He said I would not have been discharged from hospital if anything sinister was considered. I asked if I had more pain whether it was something sinister and he said yes and that they have given me a head scan if they were concerned. I took my third Naproxen pill about an hour ago. I took my first at about 6 PM yesterday and it took care of the pain within about 20 minutes. Because I had not slept at all since the pain came on when I went to bed the night prior I was suffering with it all day, but the Naproxen killed it. It wore off after about five hours and I started to feel the pain come back, but I took two Paracetamol and went to bed. I slept fine and I have had a pain-free day today, although I get very occasional pangs in the left side of my head, but only for a second. I still have the very slight dizziness when I move however. I am not sure whether dizziness is even the right word. I have read that it takes about two weeks for Naproxen to give off a constant anti-inflammatory affect that can break the cycle of benign headaches. Is this correct? I have been keeping track of my heart rate through my phone app. When I am very well rested it falls in the 60s and 70s, but my average resting heart rate seems to be 80-90 bpm. When I stand up and move around a bit it usually falls between 110-115 bpm. Is this normal? I am 25 years old and not overweight, but I do not do any exercise, which I am looking to change. I try not to check my heart rate too often in case I over think it too much, but it only seems to be 65-75 bpm after sleep and I never get it that low again during the day. Should I have any other concerns and does everything I have noted sound correct in terms of my headache being benign and my heart being fine? How much can ECGs pick up and detect? Again, based on the hospital ECG the nurse said my heart was fine other than the sinus tachycardia which I read is not harmful anyway. Is the very slight dizziness that has only really just started a symptom of benign headache? Can I expect a generally elevated heart rate from taking Naproxen twice a day? I am grateful for your answers. Thank you.