Trackpad on MacBook Air not responding

I have had my MacBook Air for 2 years now, and since last year the trackpad have not been working. If I click it respond, but there is no movement. I have been using a bluetooth mouse since it started. Every now and then the computer also flips out and the mouse is going around the screen and the computer gets "stuck", meaning I have to restart it every time. I have no idea why this is happening and I can not recall anything that I have done to cause this. I left it in for service last year and payed a high price but nothing changed. What can I do?