Why do I have brain fog and lymph node swelling?

Hello doctor,

I am a 19-year-old male, currently on no medication, and have never taken any medication. I have no illnesses that I am aware of, but I have had brain fog for the past three years. It all started when I was around 15 years old. My acne also got worse during that time. The brain fog has not resolved since a month before COVID-19 (coronavirus of 2019) hit my country. The only occasion when my mental fog lifted was one infrequent morning. Although I had only slept for five hours, I felt rested and able to think appropriately. It only lasted for around an hour until it came back. Regular brain fog has caused me difficulties in learning or focusing. When I hear or see something, it takes a while for my brain to process information. I was surprised that I could rest from sleeping since I had not felt rested for a long time, even when I slept more than eight hours. My regular sleep schedule is unorderly. I sleep around six to seven hours daily. I also have attention and memory issues. I also do not suffer from ADHD (attention deficit hyperactivity disorder). My nose has also been either stuffy or running for several months, not sure how long. I have lymph node swelling in the neck below my jawline. I took antibiotics for lymph node swelling and consulted a specialist, and they said it was not of concern. From the blood test I did a month ago, the only irregularity was my vitamin D count. I have been taking medicines for more than a month now. I underwent scans of my neck, and nothing was found. Please help.

Thank you.