Hey guys, I'm gonna try and get through the backstory quickly, so bear with me here.
So, prior to this incident, I was a month shy of my 23rd birthday, and a virgin. Not because of a lack of options, just because I'd never really cared about that kind of thing. I had to move in a hurry, and a new guy in my department at school offered to help me as he had a truck. The day after that, he stayed the night with me. Nothing happened, but that was the first time I'd had a guy stay over. He's 5 1/2 years older than me, but that was fine with me and while a bit surprising to him, he seemed fine with it too. So, after he'd stayed over 4 days out of the first week I'd been at this house, I kinda came to my senses and thought hmm, you're not really ready for this and it's kinda progressed pretty quickly, maybe you oughtta slow it down a bit. So I stopped inviting him over for a couple days, claiming I had unpacking and cleaning and homework to do (which was not exactly a lie) while I tried to think of a way to tell him I had no idea what I was doing. About a week after that, I went to a house party and proceeded to get very very drunk and I went home with him and we had sex. I did not tell him that was my first time, and frankly I don't know if he'd have believed me anyways. The next day, I saw him after he gave me a lift to my car, but I did not see him again in person for about a week. He texted me a couple times and asked if I was avoiding him or if I was mad at him or something, and every time I assured him that I was not avoiding/angry, I was just busy and that if he wanted to hang out he should just let me know and I could find time. Again, I was sort of stalling until I could figure out if I should tell him that was my first time. That didn't happen. About a month after we'd had sex, my department participated in a big competition that a bunch of schools from around the world participated in. While the other schools were in town, this guy took one of the girls from a different team home. I was a bit upset, but I didn't really think I could complain because I hadn't really pursued anything overtly. I had been trying to treat our encounter as casually as he seemed (to me) to be. Then it turns out that the girl he took home was rather large, and being a bit overweight myself I got even more embarrassed about the whole thing. Now, two months post-encounter, we've kind of gotten back to being friendly and basically ignoring what happened. I found out yesterday he's dating (or at least sort of seeing) a new girl.
So, my question is, did I do something wrong or was the whole thing just as casual as I'd been pretending it was? Keep in mind that every time he made reference to that night I indicated that I enjoyed myself and would not be opposed to doing it again sometime. At least, so it seemed to me. I know I'm not the best at the whole flirting thing, and I really have no idea how relationships work, but this time I was actually trying to make something happen. Should I have explained why I was acting the way I was explicitly? I don't really know what happened, but I feel like several steps were skipped somewhere along the line. I'm also feeling a bit hurt, as he appears to have gotten over whatever it was that we had rather quickly. It's not like he was the one or anything, it's just a bit of a bruise to the ego to think that something he apparently thought of as just a one-night stand I regarded a bit more seriously.
So, for future reference, any insight from the male point of view would be much appreciated.