What happened? Was I drugged or drunk?

Ok I know there are hundreds of questions like mine on here, but for some my story sounds different in that i remember parts of the night so vividly while completely blacking out on other parts. Firstly let me say that of course I know as an adult I take responsibility for my actions including this incidence where I drank too much. I admit when I go out drinking I do drink alot, but I've never had problems with memory until that night.I'm 23 by the way. Ok so the night went like this. I was at a friends place and we had some pre-drinks before we headed out to the club., I drank a couple of glasses of wine and skulled another bottle with my friend while in the cab on the way to the club. We went in to the club had another two double vodkas, it was around 10pm and bam i wake up in the morning next to a some unknown dude in his bed. And i know what you're thinking right now, this girl is going to use booze as an excuse for a bad lay which shes ashamed off. In my life I've only ever had 2 one night stands including this one. And I've never felt much shame in admiting I've had them cos hey it's fun. Anyway when I woke up I felt really disorientated and to be honest I thought it was kinda funny, kind of like the hangover movie all i could think of was WTF????? because there was some guys arm around me. Then I had flashes of what happened last night come bak to me. I remembered falling down on the dancefloor and hitting my *** pretty hard. I remember red drinks. i remember giggling as I came in to his house, with my friend and him trying to quieten us down cos his mum was sleeping. (yes he still lived with his mum he was young maybe 20). Then I remember lying down on his bed in his room, well i remember having sex with him and i know 100% certainty that i consented. He wasn't forceful at all and he kept asking if i was sure so there is no way i can pin this on him. Infact I think i was more forceful :S. So what I don't understand is how I can forget so much of the time and have these flashes of memory where they were really intense and vivid. I could remember everythign in detail from the way i was feeling, to the exact words he and i said. I pretty much remembered all of the sex. When I asked other people of what happened that night, apparently i appeared to be just normal drunk. I was doing nothing outrageous just dancing alot. I never feel asleep. But my friend apparently also blacked out and doesn't remember anything so I thought maybe we were drugged. The DJ said he saw us at the club all night which was 2am (he is a trusted friend so i believe him). To be honest I didn't even worry about this until i found out people can do crazy sh*t and not remember while in a blackout. I had no bruises or cuts on me apart from the bruise on my *** for falling down. I feel like I'm getting my memory back but it's more like a dream. The guy i was with that night was really nice, my 'friend' had left me and gone off with the other guy after we went bak to his place. I actually met his mum :S and he offered to make breakfast but i said i had to leave. I just don't understand why some of the stuff i do remember was so clear it was almost as if i wasnt drunk while other parts seem blurry and like a dream. has anyone had something similar happen to them?