I don't know that I have anything to add that everyone else hasn't already said, but I really do know where you're coming from. My kids started school last week, so now I feel like I have some room to breath. I know that sounds awful of me. I feel guilty saying it, but I was getting so overwhelmed.
The one thing that I've found is that if I don't get some time to myself on a regular basis I'll become very depressed. My oldest is 11, and I just recently was able to see a pattern. I used to just find myself really depressed without any knowledge of how I got there. Now, I've realized that I need at least a little bit of free time everyday to pursue my special interests, or I'll end up getting too overwhelmed. Is there anyway for you to schedule in regular breaks every week? I know it's easier said, than done, and I don't always follow my own advice.
I also know what you mean about feeling isolated. I've been a stay at home mom for about 8 years, and I really don't have any friends. It seems that sometimes I feel lonely, and I want someone to talk to, but when I am out socializing I just want to get away. People seem to irritate me. It's a catch 22. On one hand, I feel lonely, but on the other, I just don't click with most people.