Take it easy... Try to take some time for yourself. Everyone needs some time to themselves. I know, easier said than done. But even if it's an hour bike ride, a walk, anything to clear your head.
Try to get your husband to join you for a group therapy...
I don't know where you're from in Canada, but is there any way you can bring your children to daycare for a few days a week? Here in Quebec we have what's called a 7 $ a day daycare... parents pay 7$, the govt pays the rest. Everyone needs a break...
get in touch with some daycares, see if there are special programs with autistic children.
In the end, if you're not happy, your children will feel it, and they will be unhappy. The first person you gotta please is yourself. It may sound selfish, but in the long run, your happiness will reflect the people around you, and it'll make for a better lifestyle for you and your children...
Everyone needs someone to talk to, and to vent to ... Sometimes getting different perspectives on how to see things can help you put things in perspective in a less negative way. There's nothing wrong with seeing a therapist. Even if your husband won't be willing to join you, it's not something you can't do yourself.
Good luck!