C.,
I can understand your "pain" - I have 3 little ones at home (although I'm a mom of 4, well 5 if you count hubby lol), I have a full time job outside the house and go to school at night to make a better future for my littler ones (4 yr girl and 3 & 1 yr boys... my 13 yr old doesn't live with us). Yes, I do get help from hubby when I'm not home... he is a great dad, but as soon as I walk in the door he is done for the day, week or till I head back to work or school.
Your little ones are still with in "nap/quite" time age range... try to get everyone (YOU TOO) to take an after lunch nap at the sametime. That way everyone is rested to take on the second half of the day... even a hour nap in the middle of the day will help you out. And if people don't think you should... forget them. You need as much rest as you can get - take care of yourself, so you can take care of the little ones both here and on the way.
I'm glad that you see the 4 little ones as blessings... because they are. In time it will get easier!
Oh, try to get them to help you with little things... it makes them feel grown up! My 3 & 4 yr olds like to put cloths in the washing machine (we have a front loader), so that they can push all the buttons that beep, they also like helping set the table, getting thing out of the fridge (juice, milk, condiments, or even an onion when I'm cooking), and feeding the cats or dog. Eventhough they don't seem like big things, the little helps add up and save you a little time & energy and they are lerning to help out and feel proud & good and big cause they helped mommy.
One odd question - is daddy in the picture at all? Can he help or someone else even for a hour or two once a week so you can do something for yourself? Even if it locking yourself in the bathroom for a long bubble bath in candle light. Sometime small things make it better - just a few min here and there to relax... good luck!