Jenn, I feel almost certain that you need to tell someone safe what happened. Even if you made a mistake, a therapist will help you see why you behave the way you did. I could tell you many things I have done that caused me great shame until I was able to see the underlying issue that I was trying to work out. You are a child of our Creator, brave enough to find your way here for help. You are a warrior and a survivor so far. It's time to treat yourself to a sympathetic ear. THEN you can decide what info you want your boyfriend to know.
Condier this quote, can't remember where I heard it; No man (or woman in this case) can be defined solely by the worst action he/she has commited.