What is going on with my body???

It seems like my waist is shrinking...I'm now down to 170-175 pounds, wear anything between a size 32-34 depending on cut and type of material pants are made from, and I have little or no excess fat on my body. I had a very serious appendectomy, almost died as a result of a rupture and infection, about 1 1/2 ago and I can't get a perfect, flat stomach because of the way my 7 inch incesion was stiched and grew back together. Since then I don't eat as much as I used to and coupled with that I'm been really stressed out for the last 3 months because of personal issues surrounding my parents. What could be going on??? Why am I losing weight in bunches??? I sleep perfectly fine, but I'm always on the go whether it be at work or when I'm out. I'm 25 and feel like I'm healthy, I even ask people a lot whether I look thin or slim.