Why do I have severe upper left abdominal pain?

Hello. Two weeks ago, during weight training, I had a sudden pain in my lower abdominal. It was so painful that I could not move. I thought it might be cramping, but it worsened every second and in addition, I did not have any period for almost 4 months. I am 15 years old. Though, earlier in the morning before I had this unexpected pain, I had a little spotting. I have then been to the emergency room, where after 3 hours my pain stopped. I have been suspected with a small cyst rupture, however, there was no evidence indicating that the cyst had ruptured. We have done both lab works and an ultrasound and everything was absoultly normal. It is also important to mention that I had a cyst a year ago, but then it disappeared as we did another ultrasound, but for the last year I did not check it. 3 days after my pain, I have done another ultrasound and everything was fine. Another thing to mention, during the day I was at the ER, I came home and I had straight blood when I peed. The next day everything was absolutely normal without any spotting neither red or brown, everything was clear. Since then I have been having pain when I am doing sports activities and when my lower abdomendan is touched. (both left and right side). However, in the last couple days I have been having servere pain in my upper left abdomonen. When I had that terrible pain, it was mainly on the left side. Currently I am having severe pain on my upper left side, and additionally I always have a pain of hunger that feels as my stomach is sore and burns. What is going on? Can it be related to a spleen? Gastritis? Maybe there was not cyst burst?