Can you show us an example of your day and your week? It might help us to help you.
I am a very busy SAHM to 4 kids and Im 35 weeks pregnant and I'm not single so you are not alone in your struggle to stay on top of things
Just recently I have implemented a few strategies to help myself.
1) I went thru all the kids clothes and went down to bare minimums. All their clothes now fit in their drawers etc and they haven't got 20 tshirts and 15 pairs of pants each. This reduces the massive washing pile I used to end up with.
2) I spent a day getting every single load of washing done from start to finish.
3) because me washing was caught up, I was able to stay on top of it. I now only wash a load when I can peg it out (save having to rewash it!) I also peg it on the line in order. Dd's clothes,ds1,ds2,ds3 etc so that when I get it off I fold it in piles and I bring it in straight away and put it away. It only takes 15 minutes and I don't end up with clean piles of waging everywhere like I used to.
4) I think ahead. So tonight we are home and I might be having sausages and veggies for tea, I know tomorrow night I won't be home with time to make a fancy dinner so I peel tomorrow's nights veggies tonight and cut them all up ready to go. Then I plan something I can quickly cook with veggies, steak,fish,snitzels etc. this helps to eliminate some mess too (dealing with all the peelings in one go) I have prepared 3 days veggies at a time- it really helps!
Can you cut the kids activities so you aren't so busy? Carpool with friends? The kids are old enough to help. I would be insisting on them following with their chore charts or I'd be removing xyz (phone, weekend privlidges etc) until they get the msg.