I had a problem with slouching as well. It was probably a self-esteem thing, but also because I tended to carry everything with me in school which weighed me down and became habit.
The thing is, there is a correct posture, and it's not slouching. Stand up straight, shoulders back, head held high and don't look down - this is ideal. Don't think of it as "strutting" if that bothers you - I don't go for the whole braggadocio thing either. But you might as well do what gets the results you want, and besides, you can breathe deeper when you stand up straight versus when you slouch, which may help you feel better, feel more energy. And it might help the tone of your voice as well, if you feel that is an issue. I notice for example, sometimes I'll have some music on and be slouched in my chair, and I'll try to sing along but fail. I think it's because I'm slouched and can't draw in big breaths.
Also the looks thing - you might be one small fix away. I was watching a Tony Robbins video clip the other day and it talked about how the difference between success and failure can often be as small as one millimeter. What if it was just one small thing you were doing wrong, or one small thing you weren't doing that would help you? I know I feel much, much better about my looks after I shave and get a haircut that compliments the shape of my head. I was getting the wrong haircut for years and then thinking I was just ugly, but I think I finally figured it out.
Another bad habit is complaining. I have to watch myself here, very very closely, but I was a complainer for years and of course it drove women away and pretty much soured my relationships with anyone, family friends etc. all across the board. One thing I try to consciously do is avoid things that get me into a complaining binge - the news and politics for example. I try to completely avoid it. I can't complain about it if I don't know about it.
Anyway. I believe you, Bogey, can find someone. Probably a lot easier than I can. You articulate your thoughts well, you have a sense of humor, you seem like a good guy, you have hobbies that you are good at, you have enough physical and mental functionality that that can't hold you back. You're all right.