I've been underweight almost all of my life. I was a scrawny kid growing up and all the way to my early twenties. I was so thin that my hip bones were quite prominent and I had people asking me if I had an eating disorder, which I don't. If you've seen me scarf down a pizza, you wouldn't think that I had an eating disorder.
Things started to change when I started going to the gym. I put on a little weight and I was actually happy for a while. When I discontinued my gym membership (because dude, that was one expensive gym) I started to gain more weight and I lost most of my muscle definition (and then the flab started to creep in). I gained a little more weight and actually reached my ideal weight recently, which was kind of cool. Then, after being a Small for all my life, going up to a Medium made me feel fat.
I look at my arms and the muscles aren't as defined and my belly isn't as flat as it used to be. When I look at my old, skinny photos, I feel fat and unhappy when I know I shouldn't. I'm healthy (sort of if you discount the elevated cholesterol level but that one, I blame the medication), I'm going to the gym as frequently as I can, my clothes fit better and I even have some cleavage now. I can do a few push ups and even a pull up, which is more than what some men out there can do.
So why do I feel like I should lose weight?