Dealing with rude people. Help!

Why do people think that it is perfectly OK for them to touch and rub their hands all over my stomach? (5months pregnant) I tell them to stop, I explain that I do not like being touched... 90% of the time they respond with "you will just have to get used to it" or "I am going to anyways" I don't know how to make them understand that I don't like it and how disrespectful it is. I am ready to file harassment even against one of my coworkers because she won't stop. Help!