Was that suppose to be a compliment?

One day in my Civics class, I had to do a Powerpoint for this Pro's and Con's thing. Now, I chose Obesity, and went up first on the first day. I mentioned that I come from an overweight family (which is true), and I admitted that I was a bit overweight. I didn't look too much like it, I mean I'm at risk of being overweight. I've got the pounds to prove it. After my presentation, these girls at my table were like, "You're not overweight." After that was said, a black kid from behind me said, "Yeah. You aren't overweight; you're just big." My reaction was an awkward "thanks." I told this to my mother and she said that maybe he said it because I had big hips. Weird thing is my mother keeps calling me fat, and she tells me not to lose weight because I have big hips, and hat big hips don't look good on skinny women. What kind of advice is that, Mom? You call me fat and tell me to lose weight, and then tell me not to lose weight because of my big hips. Confusing advertisement.