Plan b during ovulation

26th I was ovulating; had unprotected sex; 20+ hours later took plan b. No side effects when I took the pill. Almost 2 weeks later I started to have symptoms. The symptoms continued every day. On the 10th my period was due was very light(almost barely there) my periods are usually heavy and painful. The thing is I’m over 165lbs and was ovulating at the time when the pill was taken. I’ve read stories that the pill is ineffective when this happens...it’s been 3 weeks took a pregnancy test and it came out negative?? It’s not making sense that I’m having symptoms but a negative pregnancy test..🧐