Firstly, you shouldn't feel under pressure to like or do anything you are not comfortable with. Some people are very physical in showing their feelings and others aren't; it's just the way things are. You are not a prude, because some of the examples you give are not sexual.
However, it is easier to get through life if you don't feel uncomfortable being close to people. Try to take small steps. If your friend gives a hug, take it as a compliment. Try shaking hands with adults that you meet. It's difficult to give any more advice without knowing your circumstances but remember, whether something is good or bad depends entirely on your opinion. The more that you can come into contact with people and push any thoughts that it is wrong to the back of your mind, the easier it gets. Remember, physical contact is perfectly natural. It doesn't have to be sexual in any way (think of rugby players in a scrum!) It's just a way of showing friendship.