Okay, first of all, to all of you who say "you should force your husband to get snipped": you are being selfish. Why don't you get your tubes tied instead? That hesitancy you feel towards that - I'm sure your husband has it to. In a healthy marriage you cannot 'force' your spouse to do anything, and it is a waste of effort to try. It will come back to haunt you. It takes two to make a baby, don't put it all on your man.
As to the question at hand, have you considered having your tubes tied? I know the thought of surgery makes most people anxious, but if you are sure that you will have no more children, this is the best way. It is a simple day procedure that heals fast, and you are not implementing some random foreign object that might, like several other things in the past, prove to be worse in the future by causing some side effect.