Hi Aribeth,
I am so sorry to hear that you are having such a hard time. I cannot imagine what you must be going through. I find myself regularly saying that I have the highest amount of respect for a single parent since this really is a 2-man job in my opinion! Parenting is hard and so much so if you are only one, not even to mention caring for a high maintenance child.
I can't say I know what you are going through, but my best suggestion would be to try and ask for help. Ask family and friends if they could give you a break every now and again to recharge your own batteries. We have very little support from family since most of them stay far away and the closer family is not that "close" if you know what I mean. Consider trying to find a reliable babysitter and give yourself a break from the kids every now and again. I know this is expensive, but if you look at the possible strain that will be added to the entire family if you are not re-charged from time to time it can be much more serious.
Join a religious group/church. Many churches will lovingly help and support you and many churches have support groups for single parents who are all going through the same thing.
You are in my thoughts and prayers. xx