Screen gets horizontal lines on it whenever I change the angle?

Hi everyone!

I have a 3yo Macbook Pro, and a few days ago it has started getting horizontal lines on it whenever I change the screen angle. If I don't keep it just so, the lines take up the whole screen and keep moving steadily downward. When this first started happening, the lines would just appear when I moved the screen, but now they occur if I am not holding the screen slightly towards the keyboard. I think it is some kind of loose display cable, but I read that Apple can't just fix the cable and would have me replace my whole screen to fix this. My AppleCare of course ran out in October so it would cost way too much for me to replace the whole display. I was wondering if somebody could confirm this is the problem and has any advice on how to fix it myself?

Thank you!