Bleeding after sex

My boyfriend & I had sex then after we finished I noticed blood on the bed in a few different spots. I’m assuming the blood was on his hand and then that’s how it got into the sheets??? I thought maybe his nail cut me but there was too much blood for it to be a small cut like that, didn’t make sense...The next day I was super sore & was bleeding lightly for 4-5 days (the bleeding has stopped now) but this has NEVER happened to me before. I don’t know if something serious happened or if I tore something or even how it happened... should I be worried ? Should I go to my OBGYN even tho the bleeding has stopped ? What would cause bleeding? I’m still freaking out 😅