Stand up for yourself. Do not assume you both want the same degree of intimacy. Protect yourself from a charge of rape because you didn't ask. Being drunk or stoned is no excuse. Having sex with someone who is, is rape.
Men can be victims of rape and have the same rights to counseling and legal action that women do.
Don't isolate yourself, don't feel guilty, and don't just try to ignore it. Rape, whether by a stranger or by someone you know, is a violation of your body and your trust. Do not shower, wash, douche, or change your clothes, even though that's your immediate reaction. See medical attention. If you choose to press charges, the evidence will be there.