Is my shyness normal?

I have a problem. I have always been quite shy, but now it I think it’s got worse. I am 16 and when asked in school I can’t even answer a simple question (my mind goes totally blank and even though I know the answer I just can’t remember it), putting my hand up to ask for help or to answer a question seems impossible for me and when we are told that we have to do a presentation or class discussion, I get stressed weeks before, I can’t sleep, I am depressed and it usually ends up with me actually refusing to do it. Lately, I even get stressed when the teacher calls out the morning register and even though all I have to say is ‘Here’ I feel extremely sick and stressed. I am not shy around my close friends, however I don’t even find it difficult to meet new people, except I find it hard to get close to them. Because of my extreme shyness I developed Bulimia when I was 14 and although I am getting treatment for it now I still think that my shyness was the main trigger of it and that it is a bigger problem then my actual eating disorder. I also started smoking because of it, and also cut myself once or twice. I just don’t know how to cope with this, I hate myself for making such a big deal about something so simple. What’s wrong with me?? What could I have ?? Or am I just over-reacting and it’s just normal shyness?? Thanks