Screwed up my knee last year?

Hey Im a total klutz and i live up north. It was December and the ground was covered in thick ice. I was running I tripped and hit my left knee. I cried and it swelled up for 2 weeks! (this was on the first weekend of dec. last year) I couldnt walk properly on it and it finally stopped hurting two months later. Now randomly when I walk it "moves" like its not attached to anything. I will walk and i can feel it sliding around and it randomly makes my leg give out. (btw my mom never took me to the hospital because she thinks im an exadrative baby). What do you think I did to my knee (also I lived life normally, no brace, crutches, did gym , played on my voleybal team, only limped a bit)