Why is my controller so glitchy?

So, Ive had this controller for 5 years now and it worked perfectly until last year. It just completely quit. Few weeks later i decided to try it and it didn’t connect wirelessly. So we got a cord and plugged it in.. Holy glitches. it wanted to move up and down, all the way to the right, it started pressing buttons.. so we put that controller up for about 5 months. I tried it again just a few weeks ago and it worked like a dream while it was plugged in. But just yesterday none of the buttons were working, then it did its glitchy thing again. Can this controller be fixed easily? I don’t have much money to buy a new controller and this is my only one.. HELP!