Do I have a type of anxiety/social anxiety disorder?

Ever since I was maybe about 13 years old (18 now) Ive always felt weird around people. Its like im scared to make conversation with new people because i dont really know what to say and im afraid ill mess up my words or not make any sense to them and its like so hard for me to look people in the eyes i dont know why. Ill do pretty much anything to avoid some social contact when uneccesary, even just stupid things, from getting up in front of a cl to present a project or speak, to going into a grocery store or food place to order or pay for something.Like one time in school we had a big presentation that was half our grade for the year we had to do and i stayed home from school on purpose that day just so i wouldnt have to stand up in front of everyone, so i took an F. And other times maybe ill be driving somewhere with my mom or dad and ill be starving and my parents say theyll stop so i can go in somewhere and order food somewhere and ill say no cause i dont want to go and talk to people. So ill just basically starve that day unless they buy it for me. Its like i dont want anything to do with new people.And when im in a large group I feel like everyones looking at me and how im dressed or even how i walk. Its weird. I have a lot of friends now that ive known for a while but when it comes to hanging out with new friends its so difficult for me.And when my friends I hang with invite me to hang out with them and THEIR friends too i wont cause ill feel too awkward. One of the things i hate the most is talking on the phone. I know it sounds stupid but Ive been looking for a job, and if i come a cross one where the only option is to call them i just cancel that out right away, i would have to send an application online or something. Theres a lot more to it but i just basically summarized it. But ive tried and tried and tried to act different and talk to people and i just always mess up in some way. What do you think I should do about this? Is it normal? Is it a big deal? I want to conquer this and just get over it but it seems like I cant.Hope you can help.