after sex can be come from several different sources, so it's important that you see your OBGYN. Probably the most likely of all of these sources in you is bleeding from your uterus. This is where the blood comes from when you menstruate. Given the amount of bleeding you are reporting, I wonder if you simply started your period at a time when you were not expecting it. The report of "blood all over" tells me that this might not be a small cut or blood vessel breakage. It sounds more like you started your period. If this is not the case, you might be bleeding from the cervix. The cervix has many small blood vessels near the surface that can break easily during intercourse. This is probably the most common cause of bleeding specifically associated with sex. Bleeding from the vaginal wall is also possible, though this is usually associated with a small tear in the vagina and you would experience pain along with the bleeding. I suggest that you schedule an appointment with your OBGYN. The two of you can discuss this incident and you can let your doctor
know if you are still bleeding. Your doctor will likely want to perform a pelvic exam to see if the source of bleeding can be identified. Good luck.