Post Black Out

I'm currently 28 and I believe I was r**ed in college at age 22. In the year and a half before the incident, I had started to doubt that I was straight and began having sex with other men. It got to a point where I was hooking-up with guys almost exclusively and thought I might actually be fully gay. Some of these hook-ups led to me hanging out with and befriending people in the Theatre Department, who where often LGBT or at least more accepting of queer identities than the Business Department I was in. I was invited to many of their raucous parties, which were often attended by strangers unknown to the hosts. This is not unusual for college parties as the hosts invite friends (with BYOB terms), and the friends invite friends, and then they invite friends, etc.
At the party in question, I consumed a lot of booze; as well as some cocaine, poppers, and an edible. I wound up blacking out, which was unusual even for the amount of stuff I consumed; which leads me to believe that I might have been roofied (though I don't know for sure). I woke up on my back in my bed the next afternoon with no memory of what happened later at the party, how I got home, who took me home, or what transpired when I got there. I started to piece it together though. My pants, boots, and underwear had been removed; but I was still wearing a button-down shirt that had been ripped open. My torso and penis were covered in semi-dry cum indicating that I had ejaculated. The fingers I probed into my sore asshole came back glistening with semen and a little blood. Whoever it was came inside me without protection. What was most disturbing though were the bruises, cuts, and abrasions I found all over myself. I had heavy abrasions on my wrists which seemed to indicate that they had been restrained to the headboard with zip ties or thin wire (backed up by scratches on the wood). I also had a deep and bloody laceration on my left wrist where I think someone cut me with a blade when they removed the ties (still have the scar). There were lots of bruises around my throat, so I had clearly been extensively choked at some point. I also had plenty of bruises on my ribs and torso. That part scared the hell out of me. Whoever had taken me that night could have killed me and I wouldn't have been able to stop it.
I don't know who did these things to me, or if it was more than one person. I don't know if I was into any of it at the time, gave any type of drunken consent, or how conscious I was while it was happening. I immediately got an STD test and waited for the next three days in a state of high anxiety. Fortunately, they came back negative. I had to wear a shemagh as a scarf in public for the next several weeks while the bruises around my neck healed. I was too embarrassed to make any inquiries into who took me home and I avoided any big parties for awhile. I'm sure that I was r**ed and never gave any kind of consent, since no one ever approached me about it. At no point did someone contact me or walk up and say, "Hey man, just figured I'd check in on you. Last night was hot! Let me know if you want to do it again some time."
I think the affair did have some effect on my sexuality and my habits. For the rest of college, I made a point to only hook-up with and date women as if I was trying to reclaim control over my sexuality. I've also found I'm more sexually submissive since the incident. After college, when I finally accepted my bisexuality and involved myself sexually with other men again; I found I went from mostly being a top, to where I only wanted to bottom and be the receptive partner. Even in my relations with women (including my current girlfriend) they always find themselves on top during sex. I've never really told anyone about what happened, much less anyone I've been in a relationship with. I also won't drink any beverage at a get-together that's not made in front of me or that I made myself, and I'm usually heavily armed. I think the incident has made me a bit paranoid.