5’6 and overweight?

I’m 20 and 170lbs. My doctor ASSURES me that I’m an “average” weight but I have basically 0 muscle And I go to the gym 3-4 times a week! I run on a treadmill until I want to puke! Everyone in my family is seriously obese and my aunts can’t have kids do to obesity related health issues. I want to be fit and healthy before I get pregnant, but I don’t feel that way at my current weight, even though my doctor assured me I am. Any suggestions? Am I crazy?