Almost the exact same thing happened to me.
The end of the story is that it made my bf grow up and realize how much he loved me. Our relationship actually improved exponentially following this. The key is to be honest with each other, and not to continue to make it an issue. Make it very clear that you will absolutely never accept that behaviour again, but also make it clear that you forgive him and you are able to move past it. Then MOVE PAST IT.