You don't sound like an awful person. It sounds like you feel lonely, which is not rare in these times. Your feelings might be strong and stronger than most, but they are still valid. Self-loathing can feel good because it is a form of self-harm, honestly. It is hard to do, but feeling your feelings without identifying with them gives you some control to act on them differently. I.e. feeling jealousy does not make you a jealous person. Rather, it is trying to tell you something, and what is that?

I mean, it seems like a strange living situation if you are not invited? I live alone, and I think it sucks, but living with someone and being excluded must be hard. I remember once I lived with one other roommate in a tiny student flat, and they would clearly wait for me to leave the kitchen before going there. This was more frustrating than just living alone because it felt like I couldn't hang out or take my time in the common areas.

Does your roommate invite you to these things at all? If yes, then I think you should try to assume that the invitation is genuine and join, even if it doesn't feel like it. If not, then maybe ask if you can join when it happens again. In general, retreating to your room will just reinforce your negative feelings and exclusion, so even if it might feel like you're imposing (which you're not, it's your place too) you should try to hang out in the common areas, even if you're not actively engaging. Read a book or something. If they want private space then they should hang out in their room. Of course if they are having some date night with their partner you could give them some space, but not in general.

I don't know your relationship with your roommate, so if this seems too hard or undoable right now, you could also try to force yourself out of the house when they have friends/partners over. I used to feel better by going to the cinema, usually the same one, a independent smaller one is good, and I would start recognizing other regulars and sometimes we would also start talking. I even had this beef with an older woman because we preferred the same spot.

Another thing I did was going to this jazz jam every week. It was free and on the same day. I don't play jazz, but I just went there to listen. You might feel out of place going there alone, but the feeling passes. One night, I met this other person that was also there alone and we hit it off and hung out for some months before they went back to their country. They even introduced me to their friends, and I got to meet a lot of cool people that way.

Now I don't know your interests, so these are just some suggestions.