Hello.
I am an INTJ (go to
Keirsey Temperament Website if you don't know what that is) and I score very high on the "I", which means I am very introverted myself.
I guess the main difference between you and I is that I don't see my introversion as a problem, but you do. I just want to ask you to consider the possibility that in fact, you
don't have to regard your introversion as a problem.
In fact, it may be precisely because you regard your introversion as a problem that you are nervous in social situations (and this causes you to have problems with eye contact, finding things to say etc).
I am not nervous in social situations (most of the time); it's simply that I am often just not interested in being in a social situation. Since I am not nervous, I don't really have any difficulty, say, conversing with people at a party if I feel like it. (If you were not nervous, you may not have a problem either).
Another bit of advice I have is for you to see if you would be more comfortable in social settings involving a specific activity / hobby / interest that you have. For example, if you like playing basketball, you would probably be very comfortable getting together with friends to play basketball. If you like photography, you would probably be very comfortable joining a photography club and getting together with other members to do something concerning photography. Etc.
The reason why you would be more comfortable is that your attention would be more focused on that enjoyable activity, instead of on thinking of what to say next!
As a final point, I just want to point out that introversion is probably your natural trait and it is nothing to be ashamed of. On the contrary, it confers many advantages. Highly extroverted people often seem to me to be highly dependent on other people's approval / company / friendship, for happiness - introverted people, on the other hand, can be perfectly happy all by themselves.