I have to add....that as I keep gaining I'm getting more and more uncomfortable in my own skin and get closer and closer to wanting to just stop eating. though I know I couldn't do that in a million years. it just gives you a better picture of how I feel about this :(
In that case then you may want to get a doctor to tell you for sure if its something to worry about or not. Sorry I can't be of more help.
the best type of thing to look for is toys. honestly thats the best I can tell you. look for anal beads. it looks like a string of rubber beads. the sort of thing that was designed for that. just be sure to buy lube also.