Cramp, Dull Pain In Pelvic Area Near Bladder. Transvaginal Ultrasound Done. Possibility Of Cancer, IBS?

I am having some crampy, dull pain in my pelvic area where my bladder is. It gets worse when it is full and feels better when I empty it or my bowel and when it feels like that, I often pass gas. I have had a transvaginal ultrasound back in January and other than a uterine fibroid and a shy right ovary, I was fine. My Gynocologist said it was probably IBS since he pressed on m pelvic area and could not re-create the pain. I am worried... I went from January to July with no worries or pain and then I woke up one morning and it was there. I was fine last week, and now today I have it again. Could it be bladder, uterine, colon, ovarian cancer??? Please help. I am not sure if a crampy feeling constitutes as pain. No fever, no loss of appetite, no weight loss and regular bowel movements.