D.K.
You're not alone! Believe it! I have 2. A 6yo boy and a 15mo boy. I home school my oldest and I can't get much help from DH because he's working 9 hour shifts every day with 1 1/2 hours of commuting at each end so by the time he gets home it's dinner, chores and bills and bed. I feel pretty alone and overwhelmed sometimes. Trying to juggle teaching my oldest with all of the care and nurturing a little toddler needs along with the housework and my older son's activities can be quite exhausting. Here's what helps. My DH used to work 8 hour shifts (plus commute) 5 days a week. He has since changed his schedule to a CWS (compressed work schedule) where he works 9 hour shifts and has every other Friday off. I find that this helps enormously. Just knowing that we get a three day weekend every other week keeps me going. I know that I will have roughly two weekends a month with a little more time built in and a little more help available with the kids. So I schedule the serious chores (toilet scrubbing, window washing, appliance cleaning, floor polishing etc.) for those weekends. That way I feel like I still get some of my weekend to relax. The Hubs is pretty good about wrangling the kids for me on those weekends so I feel like I can catch up and get some breathing room.
Anyways, enough about me. My point was that maybe your hubby could work something like this out, and if not, recruit your daughters for baby help. Your 13yo especially should be helping out. There is nothing wrong with requiring her to pitch in with her little brother. And your 10yo can pitch in too, but mostly with chores I would say.
Hope this helps you gain a little perspective. Get those girls to work! :)