This would be a tough case.
The fact there was blood and you friend carry you away is good evidence, but the fact you dated the guy later will hurt your case. This is unfortunate, as your dating him only made him more likely to try this again. I mean, if he is faced with the choice again - having sex with a girl who is unconsious - he will thing, "Gee, the last girl I did this to ended up going out with me, so yeah!"
You don't say who gave you the pills - was it this guy or someone else? Did someone besides this one guy rape you? Maybe he was just the one you woke up to. What was the source of all the blood? Were you a virgin? On your period? How did blood get everywhere?
What did your friend see? Did they see the boy having sex with you? Did you tell the boy you felt raped, and what did he say about it?
If you hadn't dated the guy, you might have had a decent case. The fact that you did will make it harder, but it may be worth seeing a prosector about. We need to send messages to people who do this. While the boy probably doesn't deserve to be sent to jail for 30 years when this was more of a crime of opprotunity, he does need to be punished. Just because a girl is unconsious does not give guys the right to rape her.
Please, avoid the drug scene. As you have discovered the hard way, it is not very glamourous.