Please don't bully! But i need opinions.

So....before I met my boyfriend, I'd been talking to this guy online who is significantly older than me. When me and my current bf started dating, we quit talking. But he messaged me a few months ago for about a week span. Then he messaged me again Sunday night. I just ended it with him and told him I felt I was being unfaithful to my boyfriend, none the less I never told the guy online I loved him or anything. What do I do? I'm scared. I know I should probably tell my boyfriend....but if he doesn't end it, things will never be the same. Please help me....I know I don't deserve it....but please.