What Causes Irregular Menstruation And Pain During Urination?

hi ... i keep getting these sharp pains in my stomach lately when im urinating .. of even if i pass wind ... i was kept in hospital for a night recently and they thought i had threatened appendix :( but it wasnt ! i dont know whats wrong with me and im starting to get worried ! the pains feel like im in labour ! ... there that strong at times .. they come and go .. and my periods are so irregular ! .. i cant be pregnant because i use contraception and it didnt come back possitive on the urine sample i gave in the hospital ! .. and its not a cist i had a ultrasound done :( ... HELP !!