So nervous..

I’m on heather birth control and I’ve been feeling weird lately so I took and ovulation test and pregnancy test to be safe and the pregnancy test was negative, but ovulation test was very positive. I thought I wasn’t supposed to ovulate on birth control? i was on antibiotics a couple weeks ago for strep. Does that make birth control not work? I had sex a couple days before ovulation test and the day I took the test but It was before I took the test..I’m just scared. Morning after pill wouldn’t work on me either since I’m over 150 lbs so I’ve heard.