How about giving yourself an enema & trying to hold it for a set time period? Have you ever had an enema or is that a nono? It can be most uncomfortable for you but done in the privcy of your own home it can be a real challenge. But if you don't have an enema bag the you'd have to buy one & spend the money! You should try it though, it can be very humiliating & degrading even when suffered by yourself! Good Luck with it.