To tell my parents or not to tell...

So I have super strict parents. Like super strict. I'm 21, living on my own, and my boyfriend is 25. We've been having sex (he was my first) and of course my parents don't know. I'm about to move back into my parent's house (long story) and I know that they would never let him stay the night a D anytime I go out or tell then I won't be home they have to know what in doing and who I'm with. I hate lying to them, just because I hate lying in general, but I'm terrified to tell them. Even though I'm an adult, they could still find a way to make me miserable over this. Or it could go better than I expected and they'll actually be understanding. What should I do? What would you want your kids to do?