This angers me off, and it's not even me. I know it's all been said already, but I want to reiterate: just because you know him doesn't mean he didn't rape you. Women are raped by men they know all the time. Heck, there are some women who have been raped by their own husbands. You didn't want it, you told him to stop, he did it anyway. That's rape.
I don't want to worry you more, but I feel I should point out that you don't know he doesn't have stds. Just because he told you he's a virgin doesn't mean he is, and just because he told you he doesn't have stds doesn't mean he doesn't. His actions have already shown that he's not trustworthy.
And, yes, I definitely think you should tell your mom. Don't be afraid. You haven't done anything wrong; you're the victim here. Personally, I think you should have ripped his penis off the minute he whipped it out. But, trust me, I know how you feel. I've been there. It was a guy I knew, he started something, I told him to stop, he didn't, and I just shut my mouth and waited for it to be overwith. It's easy to think it's your fault; that you "let" him do this to you. But it's not true. "no" means "no," and he's the one to blame here. But your mom needs to know what kind of people she's letting into her home. And you need to tell her that she shouldn't be letting random guys sleep in your bed. I can't believe she does that in the first place.