Imaging tests for cysts can be confusing. I had a post menopausal cyst they said was on one ovary....in surgery they found it was on the opposite ovary. They only went on US and TVU to diagnose and my CA-125 was normal...but right on the high end of normal.
TVU is a great harmless imaging test but not perfect. MRI and CT show a lot more, so if your doctor is pleased with those results that should mean you are fine.
I cannot explain the pain you are feeling. Could it more likely be connected to your prior medical history instead? Have you done anything strenuous recently that could have strained lower ab muscles?
My cyst was large by the time it was first found and I had no idea it existed. Symptoms included constipation, back pain that radiated down the leg (bad enough that sleep was impossible until Advil did its magic), fatigue, pregnant-looking bloat, and my inny belly button started to become an outy. (After surgery, it is back to inny again.) I could not eat big meals without being doubled over in abdominal pain. Also once I knew the cyst was there, I could feel it. It was fluid filled, so if I held my hand to its location while walking, I felt the liquid sloshing around in there. That's my list of things to look for if you think you have a cyst.
If you are not convinced your doctor is right, though, then try to get that follow up. Only you can tell if something is wrong from the clues your body gives you.
thank you for taking the time to reply to me.