My social skills suck

When I was younger I always thought it was just my shyness, but now at the age of 21 I'm starting to wonder if it's something else. Maybe this is why I am having a hard time putting in a good impression at my interveiws. When I talk to someone I always tense up, and I can't look at them in the eyes, and I know eye contact is pretty important. Sometimes, if the conversaton lasts too long, or it's with someone I don't know; I start to get this wierd feeling boil up like I'm going to cry. Today I had to make a phone call and I could tell I was getting this feeling, I could even hear the shakiness begin in my voice. Why? Why do I do this? I hate it, it makes me never want to leave my house or talk to anyone =(