Load up on food to lose weight?

This morning I put on a pair of cords that I had bought in Taiwan. Just as I had been suspecting: tummy is secretly enlarging, as I felt a squeeze in the belly. Since I was late for class I didn't bother to change into something else. So, I ended up being reminded all day long that I've put on some pounds!! It was uncomfortable, and I felt like unbottom my pants when I sat down. At the end of the day, I sadly donated the pants to my slimmer sister, and she very gladly and graciously received them, just like the many nice clothes she received from me when I became pregnant twice in the past....

This is very curious and rather unfair: In Taiwan, I was pigging out everyday--noodles seafood snack juices pancake you name it--worked very little and had no stress whatsoever, but I was thinner. Now, at Berkeley, I don't eat very well, I carry a gigantic backpack and walk all around campus everyday, I don't sleep well, I am constantly a bit stressed out, and I miss my hubby and soon my children. So how come I am gaining weight with all the lack of yummy foods and stress? How on earth should I explain this? I guess I need more than an Iyengar yoga class for exercise. I need to get my cords back from Shing some day!!