Could I have a social phobia?

I am having a serious problem. I haven't really noticed it until recently, but I am constantly suffering from social anxiety. I become extremely uncomfortable while around others (mostly people I don't know well) and hate crowded areas. While in crowded areas, I attempt to isolate myself from others as much as possible, I experience racing and absurd thoughts, and begin to panic and feel overwhelmed. I nearly had a nervous breakdown in walmart the other day. I rarely talk to others and feel as if I am always doing something wrong. I also feel unreasonably distressed when people I don't know well (casual friends or strangers) touch me in a minor way (brush up against me or maybe tap me on the shoulder) or even when people I've known for years become physical. For example, two of my friends and I went to a public pool the other day and I freaked out completely. One of my friends were romping with my other friend and a few casual friends ( I guess she forgot that I DESPISE physical contact) and was trying to be nice and include me. So, playfully, she decided to chace me around the pool. Well, after a while of running I began to plead with her to stop, but she wouldn't untill I was backed up against a wall. Then she tackled me, and I began to flail and scream, sucking in water as I tried to get her off of me. She finally got the clue and listened to me, and said sorry afterward, and I forgave her. Still, I think she'll listen next time. Anyway, could anyone please tell me what I should do or what could be wrong with me? Any help would be appreciated.