for your Height your weight is considerably less. was there something specific that happened in the last 6 months that you think maybe the reason for this drastic weight loss
have you changed your eating pattern? It maybe occurring because of some stress or changed eating pattern. however we may need to get a few test done like CBC and Hemoglobin
to check for anemia. TSH ,FT3 and FT4 for your thyroid
get your Fasting and post lunch glucose, Fasting insulin
levels to check for any form of diabetes
get your test reports and see a physician who can tell you accordingly what will be the next plan of action.
till then do not worry and try to improve your diet with fresh fruits and vegetables and eat at regular intervals.