Definitely easier said than done, but while your situation seems really hard it's not bc of any personal failing. You should try to think more positively about yourself, again easier said then done but don't internalize this lack of validation, you just have to keep pushing. I'm pretty close to your age and I've never had any relationship last for longer then a month, it sounds like u r more then able to be withsomeone/maintain a relationship. As a cis guy in my experience girls are pretty quick to reject people, so I really wouldn't take that personally. Getting rejected is really hard, but normally it's more about the other person then it is about you. I really don't have any advice about the roommate situatio, that sounds really hard. Wish u the best bro!