Have you seen a specialist regarding all of this? If not, you need to right away. I'm so sorry to hear all that you are enduring, and that's pretty lousy of your husband to have bailed on you like this!! You can always talk to us, we understand and do care. I was left with 3 babies and nobody, and somehow we did okay. Look into any government resources available to you and your children. What's most important is to get you better so you can care for your children and yourself. You don't say what tests you've had done, this would help us to help you. Anxiety can cause headaches and forgetfulness, but this holding your breath without any control, do you mean you are doing it and can't seem to stop? Give us a little more info so we can help. This is a great place for support and advice, and we would like to help as much as we can.
This could be some form of disorder linked to OCD. (The holding the breath part) Have you looked into speaking to a psychologist?
Did anything happen to trigger the back pain?