I don't know if this is normal but I heavily doubt it is, that difficult it makes my life.
I'm extremely nervous in different situations. If I miss a class in school, for example, I have to skip cause I can't stand the thought of standing in front of the class everyone staring at me, all the seats taken and I'd have to browse through the whole class to scan an open seat and then stumble to it, which is another adventure of its own. Another case is, yes, "performing".
I'm an amateur pianist. When I started playing, I was VERY nervous for just my mom being in the room or the next room while I played. Slowly, I got over this problem when I started to develop and got credited for it. So, our neighbour is a piano teacher and she heard that I had started playing so she came over and asked me to play something I had learnt. There's no way to describe how crap I played compared to what I actually COULD had played if she wasn't standing there behind my back paying all of her attention to my fingers. Well actually, there is a way to describe it. I'd say I played about 7% of how well I could play that part.
A couple of days later she was visiting us again, but this time not in the piano room. So I was playing Bach at the time. She had told my mom that I had advanced HEAPS. I gained confidence and started to learn other parts from other pieces (up to date, I only know one piece in whole). Now I take lessons from her and she says she's amazed how I have no problems with technique at all even with the hardest pieces.
Now I enjoy playing until suddenly somebody visits us and my fingers start to feel like dead fish! I can play, alright, no problem. Yeah sure. I know I can't play. I'm not as good as I always thought. Its just that I DO have a bad ear and I use the sostenuto pedal a lot to cover up the ugly mistakes I do sooo often. I am ridiculous interpreting Bach romantically or trying to make Prokofiev out of Rachmaninoff etc. Playing piano is really the primary thing I like to do in my life, yet I'm quite crap at it. Now if the visitor would be just about to leave the house, I start banging with 102% confidence grunting in my mind "Check this out I own the World!". Usually it works out fine, I've exceeded myself. Still I'm left alone with the thought of cheating myself about my level of skills. This lack of confidence follows me about everywhere, not just about piano playing but about most things. And of course they add up to each other!
If I ever want to perform anything in front of an audience, I really need to get over this. I don't know what else to do, but slowly tricking myself into "performing" situations and that way build up confidence to speak through the instrument instead of just thinking about every possible way to mess up each second.