Period, Pregnancy, Meds. Oh my.

Hello all,

My last period was March 23rd. I am usually a 28 day cycle. November-February periods were weird so my gyno put me on provera for 10 days to induce my March period. About 5 days after the last pill, I got the period it induced. I was due for my period on April 20th but didn't get it. I had noticed my breasts would feel like there were "twinges" happening (weird I know.) on the 21st, I wiped and there was light pink blood. Nothing else has come of this. I did notice that when I stretched my uterus had a weird pulling sensation. Thoughts? Also took a pregnancy test yesterday and it was negative.