It's a good story, well done. The descriptions are great. I do like the current, camping thread. Very horror movie-like.
Plotwise I think maybe things happened too fast, sometimes it can be good to draw things out. And otherwise the protagonist was fairly empty, just a fat horny guy. As you can see from the name of the forum there's more intimate relationships that can be taken advantage of. Not all bullies have to be huge tough jocks, after all, some can just be huge fatasses. Doesn't have to be a bully, of course, could be a detested cousin, a teacher Jason got fired, doesn't have to be an enemy, either, maybe just some fat friend of Jason's that never really liked him but always wanted to pound his mom. Either way, someone with a connection and background. Having a back and forth where Jason sees his hot, successful mom falling for Richard but not -bam- instantly a bimboslut could be a good way to build it. Maybe Dick can only make small changes, one a day or something. Jason has to find ways to interfere (until Dick uses some of his days to keep Jason distracted, could be even turning him into a girl, or making him go try and have sex with all his friends, or Dicks friends).