Please help I could use some advice...never too thin...?

Tonight once again me and my fiance got into another argument about my weight. We have been together about 3 years and I think about 2 years ago I was down way to thin you could count ribs. But to me I never thought I was to thin. Well he got me to start eating again and I went from 155 to 220 over the period of about a year. Well last week my daughter turned 9 months old and I'm finally back down to 196. My fiance said tonight every week I'm lookin at a new diett atkins, weight watchers, green t, etc. Right now I'm doing the 6 week body makeover which I think is pretty healthy. Any suggestions on the situation? Have you or anyone you know been in this situation?