How do I get over this? [read details]?

It’s called stage fright and is very common. There are coaches who can teach you some tricks and possibly hypnogtherapists. Ask around in your music community; there will be lots of other people who will know what you are talking about.

Most performers have some degree of stage fright.

Managing stage fright

edit; hypnotherapists

I go to a very musically oriented class… A lot of my closest friends play music and have talked to me about the same problem, so I think I understand your situation. :) So you are definately not alone with this problem!!
The first thing you might want to do is try to figure out why you are so getting so nervous- are you worried people will judge you? Are the songs you’re singing too personal?
If you feel like theres too much pressure singing to people one on one, maybe you could try singing in less formal circumstances, try singing karaoke with your boyfriend or something to get him used to your voice, maybe you could fool around and ask him if he wants to make a song with you, sing along with songs on the radio with other people present, join the school choir or something. :)

But ultimately, practice is key. Just throw yourself into it, in the end you’ll be amazed you were so scared in the first place.

Most performers face the fear and do it anyway. Some still have nausea and vomiting before the show and then go on stage and are brilliant performers.

There are methods to reduce the anxiety but nothing will eliminate it completely. For some, hypnotherapy works perfectly.

Practice, practice, practice in front of people all the time.

Trust me when I tell you from experience that stage fright doesn’t have to be your foe if you learn to make it your friend by doing as @marinelife suggests. Practice will help you tame that energy and it will keep you sharp. I’ve made presentations in front of many large groups and on the occasions when I didn’t have or repressed my stage fright before and during the performance, I was sub-par. Ask any actor how he/she feels about stage fright and you’ll hear the same thing.

Try singing with another person before singing by yourself.
After you get enough confidence you will sing on your own with no problems

Thanks, everyone.. :)
I’ll try to play and sing in front of many people until I don’t care anymore.. it sounds so easy but I know it’s so damn difficult.. but I’ve done a lot of things that were scarier than this.. so why not try?