Bleeding during fingering

My boyfriend and I were very horny and he would finger me a lot and aggressive. The last two times we did I would bleed during but not before or after. The first time it was quite a bit and the next day seeing that I didn’t bleed I didn’t think but of it. The second time it wasn’t much. Mostly spotting. I finished my period on Monday so I just assumed it was dried blood. I did start birth control on Sunday so I was wondering what this might be.