Hi Anne,
Are you married or do you have a significant other in the house? If so, then give him some responsibility. You don't have to be the one to do it all, all the time. That said, I understand where you're coming from. I'm also a full-time mom and have a full-time job (I work from home) and while I only have one toddler at this point, I too get overwhelmed by all the activities, the housework, walking the dogs, keeping myself organized and figuring out a time to relax. Here's what I do:
I try to take about an hour every night after my little one goes to bed and do something around the house. It could be cleaning something, doing a load of laundry, whatever. Once that hour is up, I sit down and relax, read a book, take a bath, snuggle with my husband on the couch, whatever. I find that if I stay on top of things during the week, then the weekends are much nicer and I can relax more. Plus, since I'm doing these chores after my daughter goes to bed, that gives me a little quiet time by myself to do the things that make me feel a little less scattered and more in control of life (even when it seems to be chaos most of the time!)
That said, you also have to realize that housework isn't ALL that important. Time with your children and family is the most important thing. They're growing up fast and you don't want to miss it because you're scrubbing toilets. Perhaps the best idea is to spot clean yourself and then have someone come in to deep clean your place once or twice a month. If you have the money for it, it could save you time and stress to do that.
Maybe the best thing to do to organize the rest of the activities of your life is to just make a calendar and refuse to do more than one extra thing each day. Whether it's going to a soccer game or going out with friends, taking the dog to the dog park, whatever. Plus, if you see what's coming up for the week, you can settle with it a little more than you would if you were just running around like a crazy person asking what's next. :) Just remember that it's important for you to carve out time daily for you. Just you. Even if it's just for an hour. That healing and recharging is the best thing you can do for yourself and your kids because it helps you be your best for them. And, it gives you something to look forward to daily even when things are nuts.
Regardless, just know that many of us feel your pain. Best of luck to you!
Hilary