Stage Fright

I have had to deal with this sort of thing since my freshman year of high school. I remember when I first made the Varsity Pom line at my school, and I was so nervous to dance in front of the whole school. Towards my sophomore year, it didn't bug me anymore. Is it because I just kept performing repetitively? I have no problem getting up in front of people and dancing- and I sell it, too. How can that be, that I am frigid and shaky when I have to play even a simple etude for my violin teacher or even a piece for an audience, but then I can go out on a stage and dance away?
I never used to be scared to play violin in front of others, nor get nervous. Since my freshman year though, it changed. Now, I can even mess up on a simple scale in front of others. It is so irritable to me, because I will practice so much, and work hard. Then, I get to my violin lesson, and it is as if I am playing the etude for my teacher like it's the first time I'm looking at it. It is so annoying!! I can't get over it. I practiced for almost about three hours today, mostly on my etude, not much on the piece. I got to my lesson, and immediately began to mess up after the SECOND measure! I then harbor these feelings, thinking, "maybe this is a sign that the music world isn't for me-it's not going to get any better."
Is it?
I play the pieces and etudes I am required to practice each week almost flawless by the time I have to go to my lesson. I play the best when I'm not performing for someone, or for my teacher.
I wish it was different... I wish I could just- be one of those people who has no problem playing for people, and likes to. Almost as if it's showing off. But, I'm not like that, and I sort of wish I were. I mean, it's not like I haven't been playing violin for 14 years of my life. You'd think I wouldn't get stage fright.

Dear God, whatever god people believe in. Who ever is listening up and out there:
Wash this horrible 'curse' away from me. It's hindering and delaying my progression in music.

Thanks.
xoxx