If you really don't want a 4th child then definitely go and get the MAP. Might save you from a much harder decision in another few weeks time. TBH I don't agree with the whole "DH can't be cranky, he was there too" comments. If you and your DH have agreed not to have another child, then its not really fair to turn around and expect him to be happy about it. If you aren't entirely sure of your cycle then there's no way he would be. My DH and I are actively trying for a baby and he wouldn't have the first clue as to where I'm up to in my cycle most of the time - he just realises he's getting lucky more often

But if this is what you maybe secretly want but just haven't voiced to your DH then this could be the time to sit him down for a serious chat and at least give him some role in the decision making of whether or not you just wing it and let whatever will be will be.