What could be wrong with my leg?

my knee has so much pain in it say when im bending down or simply walking up a few steps it is so painfull and i have the same pain in my ankle now(same leg, left one). its crucial for me to walk up steps and down them cuz our laundry room in the apt building goes down a flight of steps ive even had to have my bf help me because it hurts to walk upand down them. i have an apt in nov. to get a check up.. but untill then please help im only 24 im not over weight there is no pain in my calf but my shins hurt on occasion and get random bruising for no reason that wont go away for weeks and they are very small and tender bruises whats going on with my knee ankle and bruising please help!! :(