My controller registers buttons I didn't press

When ever I use this controller, it always "glitches out" I was playing MW2 today and I was constantly changing weapons (Triangle) even though I didn't press it. Then it got more rigorous and I would start shooting (R2) when I didn't press it. I would also throw flashes (L1) without pressing it. This started to happen after I had opened the the controller a couple months ago.