Hello. I am 15, 5 6 and 125 lbs. a while ago I went to the childrens hospital due to the fact they thought I had RA, which I do not, and it was due to my depression, stress, anxiety and low vitamin D. lately in the morning I realize My knees feel very weak for about an hour or so. I don t play sports and im not very active. whats wrong? this has been happening for about 3 weeks.