rape help

I had my ex boyfriends best friend invite me to a party at his house in October, he promised my ex would be there so I went to try and rekindle things. I showed up, had one drink and don't remember anything. I woke up the next morning naked in his bathtub, and he told me I was all over him and then we had sex. 
I brought my now ex best friend with me, and she left me there to hook up with some dude some time that night (hence the ex best friend label). 
Over the next few days, she filled me in on how messed up I was (only having ONE drink HE made), and crying over my ex to his friend, and filling in all the blanks. 
Long story short, I'm 80% sure he put something in my drink and had sex with me without my sober consent. 
I didn't do anything about it, and only told that friend. But now it's killing me. 
Is there any way I could take legal action, even though it happened in October and I have no proof? I feel absolutely disgusting, and knowing he's still out there sickens me.