Bleeding after sex

I had sex yesterday for the first time in ten weeks. We had plenty of foreplay, used plenty of lube, my partner isnt extremely large, we weren’t in weird positions, we weren’t very rough. Yet for some reason when he pulled out to change positions (from missionary) there was blood everywhere. It wasn’t my period (haven’t had one since July 2018 - I have an iud) and it was significantly more than spotting. I’m now incredibly sore and in pain constantly. I think I tore the bit of skin right by the vagina opening but I’ve done that before and never bled like this. I also think I’ve hurt myself internally and I’m very sensitive and sore

Does anyone know how this might’ve happened?? It was nothing out of the ordinary for us, in fact we were quite vanilla by our standards, and I don’t know how I’ve managed to hurt myself so badly. I’ve never been in so much pain after sex, and the internal pain is completely new for me