Chronic Knee Pain: Seeking Advice

sorry for the long post in advance I need help. I injured my knee twice in middle school (2013-14ish). the injuries were treated with some delay due to my own negligence of informing my parents. but now I am 21 and still have so much pain. it swells to the point it bruises. the pain gets so bad I can barely stand and it buckles randomly. I keep going to diffrent doctors and I always get diffrent answers on what's wrong and diffrent treatment plans and nothing has helped. the pain has been nonstop for a bout a month now. it usually just comes and goes if I'm to active but it's been constant. I also have a swollen lump on the side on my knee. I'm at a loss and don't know what else to do.