Sex gone wrong

About 4 nights ago I was having sex. All of a sudden it felt like my partner hit something and a sharp cramp took over my abdomen. I went to the bathroom and sat for a second until I could urinate after I did I felt a little better. The next day the pain was still their and I started to bleed heavily for two days. The bleeding has stopped but the pain in still here. Everyone keeps telling me it will last but I don't know what to do. Can someone give me some advice?