Why did i bleed during sex? i've got no stds, it also wasn't my period, but there was quite a lot of blood, i've also got lower abdomen pain afterwards.

Blood=tissue damage: Any active non-menstrual bleeding/spotting you have after intercourse would reflect some type of injury to tissues exposed to the mechanical forces involved. You might see a small bleeding site with a close self exam (lighted mirror) or a doc could locate the site. If it is minimal and you keep the areas clean it will likely stop.If you are soaking pads you need to be evaluated.