claire,
My girl is a BBW. I wouldn't have called myself a chubby chaser or BBW fetishist before I met her, although I've always liked curves, but when I got to know her I came to see her size as a big turn-on. There's something really exciting about dominating a woman who's more than twice my size, and I love that I can just sink my fingertips (or teeth, hehe) into just about any part of her. With her white skin and long, curly red hair, she looks like a woman in a pre-Raphaelite painting. Usually one of the ones where the women are being ravished.
Sometimes people are surprised that I'm attracted to plus-sized women because I'm on the athletic side myself (I wear a size 4 or 6 and am a bit of a gym rat). I think there's a really pervasive attitude, at least in Western culture, that being fat or thin says something major about who you are as a person, and that if you're thin it must be because you work really hard to be that way, or if you're fat it's because you just sit around on the couch all day and don't care about your health. I really don't believe in that -- I don't think that body type has anything to do with who you are or what your priorities are. I know that I don't work to be thin; I eat more than most heavy people I know.So it would be pretty lame for me to judge someone based on their weight. In fact, I think it's pretty lame for anyone to judge someone without knowing the first thing about them, which is how lots of people treat heavy folks all the time.
It sounds like you're lucky to have found someone who wants to make you feel better about yourself, but in my experience confidence really has to come from within. Seeing a therapist helped me when I was having some body-image problems, so it might help you, too. And if you do decide to lose weight, of course that's your choice, but please resist the pressure to do anything extreme or unhealthy. Starving your body can cause long-term damage; I know people who've had serious health problems caused by extreme diets. Remember that you are a person who is loved and valued, not some source of shame or "concern" that has to be "cured."
I hope that my response helps.
~Hime