I Hit My Head Two Times In The Same Spot

i hit my head two times in the same spot in one day. i got a lump and started losing hair around the area. the pressure became so severe i went to the doctor 2 weeks later because the lump got bigger and they drained it (yellow liquid came out) and gave me antibiotics. it is back again and is starting to hurt i went to the ER and they went to drain it again now its been a month and it was clear fluid. what can this be?