Gym Problem!

Although I am enjoying losing all the weight, I am having a problem at the gym. I go and work out, shower, and begin to get ready for school. The problem ,you see, is when I go to put on my pants. They seem to fall right back down. Twice this week I had that problem, because the pants that I chose to wear, I didn't try on before I went to put them on for the day and I hadn't worn them since this past winter. Monday's pair of pants didn't have any belt loops, so the make shift ribbon belt was constantly moving around and I ended up rolling the top down so that it kind of stayed. The pants on Friday hung on my hips, but by the end of the day I could put a 33oz bottle of water down through the top of my pants and out the bottom with my leg in it.