I suck (reason 4,673)

I never came up with anything to do today. Instead, as you might guess from the posting frequency, I just wasted time online. Most of my housemates are out at parties tonight. I was wondering if I needed an excuse not to go, but I guess nobody expects me to go anymore, and staying in my room was probably enough indication that I wasn't going anywhere. One of my housemates invited people over for dinner tonight and I was thinking that would be an excuse, but I was somewhat resistant to going. I ended up not replying to his email since I figured I'd see him at some point, but instead it turned into me just never responding. So now I'm still in my room and afraid to go out because then I'll have to confront (in this case, confront means "be seen by and possibly have to say hello to") the large group of people in the dining room. So now I'm being incredibly rude by ignoring them all and having absolutely no excuse as to why I didn't join them for dinner. And why didn't I join them? I'm not quite sure... I have weirdly ambivalent feelings about being invited to these dinner parties.
Housemate L. often has large groups of people over for dinner and ever since last summer, I'm pretty much always invited. I'm not entirely sure why. I suppose the most obvious answer is that he likes my company, but of course I'm not convinced. As with pretty much every other situation, I barely say anything and just sit there feeling uncomfortable - why would anyone enjoy being around that? The explanation that feels more right to me is that since I never go out and do things, he feels an obligation to feed and include me (which is consistent with his stated reasons for inviting certain other people on occasion). For this reason, I end up feeling even more uncomfortable than I might otherwise and then even though I desperately want to be by myself for a while and/or go to sleep, I end up staying up to clean up because there's no easy way to make an exit from a dinner party when you live in the same house. Plus I feel like I have to justify my presence by helping cook and clean up, since I'm only there as a charity case.
I've been on a couple of trips with L. mainly because the two of us are the only ones who ever seem interested in travelling to the places we go. Then I end up feeling like I have an obligation to be entertaining since he's stuck with only me to talk to, but I just end up feeling guilty and embarrassed at all the silence. He's pretty quiet too, but usually ends up talking more to make up for me. He's tried to ask why I'm so quiet sometimes, but I'm an expert on deflecting questioning.
I like L. for the most part. He's a fellow non-American and has a good snarky sense of humour, but I feel incredibly ignorant and slow around him. He doesn't mean to be pretentious, but he pretty much only reads classics and likes to tease me about reading science fiction and graphic novels (actually, just not disdaining them would be enough to tease me about). I'm already insecure enough about admitting things I like so I get defensive easily.
Actually, the teasing is something I really don't like. I know it's light-hearted and not meant to be taken seriously, but it does feel like he's belittling things I'm already sensitive about, like killing mice for research purposes, taking 10 years to graduate, not being well-read enough etc. Maybe it's just too close to the way my brother used to tease me mercilessly. The difference is here I know it's meant to be friendly, so I can't object without overreacting (and with my reputation for being as easy going as a doormat, any reaction would be taken as an overreaction) so I feel powerless to defend myself, and also that what he's saying jokingly is true, because it's what I already tell myself. Maybe I'm just not used to being teased by friends. For some reason I always seem to be off limits for teasing (people would apologise to me for things they wouldn't think twice about saying to another friend). It's another thing that made me feel like I didn't ever fit in, not that this is any better.
Really, the reasons I feel uncomfortable are all to do with me, not him, so I feel bad for rejecting invitations and not being more friendly. I feel like a petulant child. The other thing is, he's not the most socially adept either, but he still manages to invite people over and befriend people, whereas I just wallow in my guilt at not making an effort. Maybe I'm just resentful that he's so much smarter, better read, wittier, friendlier etc than me.

I keep hoping that the process of writing one of these big rambly posts will help me figure something out so that I can change my behaviour, but I guess no amount of navel-gazing can substitute for actually doing something...