Hi about this time last year me and my boyfriend had sex. I was not a virgin but I bled very bad. This has continued. Not all the time we have sex but most of the time. What could be causing this?

Needs eval. Bleeding is a sign of tissue injury. The vaginal wall of a post adolescent female is estrogenized/toughened enough to handle intercourse.If you are bleeding, there is some form of tissue tearing, so you should have an evaluation to see where the blood is coming from.
One of those times. There are a number of causes for this but this is one of those times where you need to go see your doctor. This should be evaluated and you need to be seen. Good luck. I may not be anything serious but get it checked.