Having the urge to urinate a lot. had a pelvic exam and vag u/s 5 months ago. uti ruled out. could it be ovarian cancer?

Requires recheck: 5 months is a long time of gap to entirely trust for sorting out your present problem. Your symptoms require a recheck up Now. You either have a UTI or something pressing on your urinary bladder. A Pelvic Ultrasound may help to find the cause. Otherwise you should be examined with the aid of a CT scan of the pelvis

Seems unlikely: Ovarian cancer would not be my first thought in someone with urinary urgency. Overactive bladder and interstitial cystitis are common causes. An obgyn visit will be needed to help sort this out and do the evaluation. If needed a referral to a Urogynecologist may be helpful.