What can be the reason for cramps during pregnancy?

Hi doctor,

I received a couple of faint positive pregnancy tests two weeks ago. Then, I went to my primary physician for another urine test, which came out as negative. Later, I felt some cramping on and off all day on my left side. The cramps were similar to premenstrual cramps along with sore nipples, increased saliva, and sense of taste, absent-mindedness, forgetfulness, very noticeable fatigue, occasional backache and headache, indigestion, burps and frequent urination. I was anxious and read about ectopic pregnancies and decided to test that night. It was a darker line than the previous tests and the result was pretty fast. When I tested the next morning, it was even darker and the result came very quickly. Then, two digital tests a couple of days after being positive. What can be the reason for my pain? Can it occur from a corpus luteum cyst and pregnancy? Is it safe to say that I am pregnant because of the tests becoming darker? Or were they possibly all false positives? I feel like the cramps are a bit more spaced out and less frequent now. Also, there has been no bleeding. I have my first appointment scheduled 15 days from now, but I am hoping for a little insight. I am currently on Vitex capsules 400 mg, GNC prenatal vitamins and fish oil pills. Thank you.