**Edit: Yay! I'm happy TK knows what I'm talking about (about being chill for the interview, not caring, not making a big deal, etc.) Oh yeah! I forgot to mention, when you apply, call the job multiple times and ask for the manager to schedule an interview. I'd say call two days after you turn in your application. It looks good even though it seems annoying.**
1. You're not an idiot - don't be down on yourself. That's what holds you back.
2. I used to be VERY anti social. To the point where people hated me and it took me forever to get a job. I have horrible anxiety that I take no medication for. I learned that job interviews take practice and I got good at them by doing a lot and failing so many times. I'm not saying that you will fail, but if you do do badly, NEVER regret it. Every failure is a lesson learned and it adds to yor experience.
3. Not to brag, but I am great at interviewing now. My best advice is to practice by doing a lot of interviews (that's the shitty part) - but when you do this be confident and if you're not confident, pretend you are. Fake it, sell yourself. This seems daunting, I know, but what helps me to act confident is making sure I'm energized and comfortable. Drink a little bit of coffee and eat a good breakfast and always try to schedule your interview in the mid morning. 10-11ish? That way, you don't have the whole day to worry about it. Be comfortable by dressing in something plain and business casual (usually depending on the job) - some nice plain slacks or business pants, a plain shirt, some plain black or brown shoes. If you get hot or cold easily, dress according to your body type. For some reason I get anxious if I wear short sleeved shirts so I always go long sleeved.
4. Do your research on where you're applying and look up "interview questions for ...." - some websites actually have people post questions and also look up general interview questions and practical them. This doesn't necessarily mean you have to recite and lie (even though lying can be necessary in an interview) but this is to have the answers already in your head so you can reference them easier. Also, I started being offered jobs a lot more when I stopped stressing about getting the job and being obsessed about failing or doing well. This will be your downfall. In a sense, stop caring. Just think to yourself: " if I don't get the job, it's good because it will be another experience and another lesson." Either way, you win so just don't stress about it. Don't think of all the possible worst things that can happen cause that will only hurt you and overwhelm you (plus we anxious people always expect the worst when it's actually not that bad).
I still suffer from bad anxiety but I've come a long way and I know you will too. But the only way you can over come these things is rewiring your thinking into positivity. Ignore negative, angry, and scared thoughts. Let go and let yourself not care a little. It's freeing and you need it.