even tho this was posted a while ago, I feel I that i must write and say I go through exactly the same thing. I love to sing and think i do it pretty well, but put me in front of someone, my throte gets tight and my whole body starts to shake, this dosent do much for my singing career. Cant really offer you any advise as i'm not yet passed it either, but I will say keep at it, put your self in a position, join a singing group and sing in front of people as often as you can, you WILL get over the nerves, and realsie that the buzz you get singing infront of people doesnt eve nearly compare to that of singing in the shower!
Take care, and good luck!