Hmmm, I'm pro - choice but the comments re: that choice in your situation are ABSURD. You just need time to come to grips w/ having another child... as others have mentioned it may take the whole 9 months to do so.... but it will come.
Is 5 children a lot - yes, but not a ton of children - you're already playing zone defense as it is, so what is one more??
Re: your older child - I'm sorry for your issues with him and I hope that you get the proper diagnosis and help - if he's 6.5 and you're just now getting help that tells me that his issues can't be that over the top b/c he would have (at the VERY least) been flagged at pre-K screening ... so I think that you're just overwhelmed with ALL that is going on and that once you've got a few answers for your son and him on the right path you'll be able to feel better about all of this. Do, however get your hubby to a Dr. for the big V and have the Dr. tie your tube after the birth (my neighbor had number 6 AFTER her hubby's V.).