This one comes from the site coiledfist.org. If you aren't familiar with that site, it is mostly a size fetish site, focusing on macro and microphilia. With some digging you can find some fun stories with some hot muscular blokes as well.
As such, this story may not be for everyone (very few stories are!) but if you are into size changes and seeing big muscular roommates growing even more then you will enjoy this one.
THEMES: Growth, shrinking, humiliation, macro, micro, domination, college