When I play a song thats long, my arm starts hurting and it feels like i need to put my arm down cuz it hurts...Is it cause im left handed or sumthing? It really annoys me..and my concert is coming up. Anyone has experienced this? Why does this happen?

Which arm?

You mean your right arm, don`t you? The bowing arm. Anything we do that creates effort can hurt, or not really "hurt", but lead to soreness & fatique. You must keep the arm up as horizontal as possible, try to leave the elbow at 90 degrees most of the time, but not "frozen", and move mainly from the shoulder.

It is NOT easy. You may find this is even harder. THEN it gets easy.

If this is wrong, believe me, I want to know about it! Anybody who can correct me, please do; we have experts here with dignity and poise, unlike in some other tinny instument sections. And our goals are the same. theoneandonlybowfrog

We are told to keep the arm down, only `open` the arm when there`s a need to open the sound.
The main focus should be on your elbow. Don`t move it in and out.
Then comes the shoulders, drop them down naturally. And that`s the way they should remain when u play the violin.
Give your body weight to the ground and onto the violin, do not `contain` your own bodyweight which always leads into tension and uneven tone.
If tension is on the left, then don`t clasp or grasp. And palm away from fingerboard.
If nothing else works, check yourself in the mirror when u play, and you`ll realise what is wrong.
If not, enroll in Alexander Technique lesson.

My left violin position arm hurts..not the right hand

oops, sorry wrong sn...lolz..
by the way its my left hand that hurts..not the right hand

I used to feel this too... how do you hold your hand when you are fingering? I found that when I dropped my wrist (I`m sure we`ve all heard that before! )That my arm was less tense and I was able to play longer and I didn`t feel the pain.