I Have Never Had High Cholesterol, However I Have Had

I have never had high cholesterol, however I have had a heart attack and my Dr. put me on Lipitor...now I can't maintain weight (5 ft 4 in and weigh 100 lb) my cholesterol HDL 60, LDL 40 Is the medication needful?
My older sister (I am 71) has had a heart attack, my mother died of a heart attack - both weighed at least 60 lbs more than I (my father was very thing) I have high metabolism...