Do I have Social Anxiety Disorder?

whenever I'm at school, or anywhere for that matter i never feel comfortable and feel like everyone is like "look at that kid he has no friends"...im very akward when talking to other kids and try my hardest to dodge social situations I go to college though so its not easy and time after time I embarrass myself whenevr I have to talk. I do fine with adults though and can speak to a cashier or ask a question at a store or something. very bad with girls and now I just try to avoid them at all costs. also I hav this weird thing that happens..when I smoke weed I get these thoughts of whenever I'm somewhere everyone is watching and analyzing me like they know I go home and do nothing and that there's some kind of inside joke about me around campus. do I have SAD or is it something else? or am I just shy?