I'm with Skella. Having sex with someone you just met that night and you were completely blacked out, not likely completely consensual. You were taken advantage of. Period.
The trouble is, your BF may not be as understanding about this as someone who has been through it themselves. I do think timing is important and I wouldn't wait too long to tell him. He is going to be wondering about his safety regarding STD's. I can imagine you are having a very hard time trying to hide your anxiety and stress. If he knows you like he should he has probably already sensed something is wrong.
Can I make a suggestion? Please don't put yourself in that situation again. Many people who have been victimized once will be so again. Don't let that happen to you. Don't put yourself in that position again, and DROP THAT "FRIEND". She did you absolutely zero favors. She should feel like an a- hole.
Please take this as a very very very serious warning sign. Stay with us on SR. Be well