Social Anxiety and other issues

It's bad that I have social anxiety. It's even worse that I'm not intelligent. How dumb I really am is really starting to show. I feel like I just don't "get" it or anything. I don't have any friends. The ones I had or who tried to befriend me, I caused them to shy away. I have a boyfriend though. Every time I find someone new I end up ruining the relationship. I just "oops..." let's try it again, again, again, and again. My relationship right now is not that awesome. My boyfriend and I have been dating for like five months. We only talked on the phone twice (long distance relationship btw) and mostly just text. I'm nervous, terrified when it comes to talking on the phone. Even though we've dated for awhile. It's kind of awkward because we only text. It's like I'm talking to a entirely person. So I stutter, my mind goes blank, and yeah.

That happens partially because I'm nervous and can't express myself clearly. My vocabulary, social skills, and speech could be better. I can't even comprehend what people are talking about sometimes. They use words, talk about events, and things I'm not familiar with. It makes me feel so dumb. People call me immature, that I'm a 13 year old in a 16 year old body. Even my family makes fun of me along with them.

I try to just not care and improve myself. I just wanted to post here and see anyone could give me some advice/tips.

Read a book. Youth don't read enough these days, because of television and the like. Books are incredibly enriching in many ways. They help to increase one's vocabulary, to learn new things, to better understand our world, etc. Plus they can of course be incredibly fun by taking you on amazing journeys. You could also try reading the news to keep up to date on what's happening in the world. Knowledge is power.