I'm scared.. My boyfriend is confessing *10 points*?

It hinges YOU from letting your relationship grow.... not him. You are the sole reason here girl. You have to let this go or it's going to destroy your relationship. His past is exactly that.... it's his, not yours. He can still talk to his ex and share a laugh... so what? She was a part of his life at one point, a big part.... just as you are a big part of his life now. As I said, if you don't shelf this, your relationship is going to suffer big time.