Feeling Overwhelmed

I've been so overwhelmed lately that the little bit of joy I had left in life has been sucked right out of me. I feel like I never getting anything accomplished with my dc where school is concerned. There are a lot of moments throughout the day when I just think they would be better off back in school. I think to myself, what are they learning here at home? The only thing that gets done a regular basis is math and that hasn't been happening much lately either. I have a very demanding 4 year old and 1 year old, as sweet as they are as soon as I sit down to do something with the older two something happends to upset Sweetie Pie and then I find myself having to scream the lesson to the older two so the can hear me above her cries. I find myself wanting to push on even with her crying because I'm afraid if I don't we will never get back to it. I just don't feel like I have ever been able to get it together enough to be a good mom and teacher to my dc. No, I really don't want to send them back to school but I can't figure out how to get past this. I'm afraid that they are falling further and further behind and there is nothing I can do to stop it. I feel myself falling into a depression from being overwhelmed with the kids and because of some other things that are going on in my life right now. I sometimes think we should just take a break from 'trying to homeschool' but I've been doing that on and off since we started and nothing has changed. I just don't know what to do.