This is a difficult situation. I can’t give you a concrete answer but I’ll do my best to help.
First and foremost, know that it wasn’t your fault. Whether you “initiated” sex or not is inconsequential given the fact that you had consumed a large amount of alcohol. Your casual friend should not have had sex with you, regardless of your actions toward him.
Second of all, even if you’re unsure whether to consider it rape or not, given your age he did commit statutory rape. You can take legal action against him, as his actions were illegal.
Talk to someone you trust. If you have older friends that are knowledgeable about matters and will probably support you, go to them. Go to a counselor, too. A family member that won’t judge, a friend’s parent, just talk to someone about it. But if anyone tells you it was your fault, or just to ignore it, they’re wrong. Don’t believe them and don’t let them talk you out of it. If you feel scared by a sexual encounter, it isn’t normal drunken sex regret, it’s a problem and you need help.