Does your husband help you with some of the household chores?
I'm a working mom, so I have to try to keep up with things in the evenings/weekends, and it's tough with a 4 year old (tomorrow) and a 2 year-old.
My husband have naturally evolved over time to split the chores around the house. I do most of the cooking and kitchen cleaning (dishes, floors), laundry. He always takes the trash out, does most of the vacuuming, helps me sweep the floors. He's getting better about identifying that things need to be done (like wiping down counters) and is always good about helping when asked.
We got some cabinets (with doors to hide contents) and some colored bins from Target and keep a lot of the kids' toys in there. The colors of the baskets indicate the contents. Green = coloring books/crayons, Blue = Transformers/Legos, Pink = kitchen toys, etc.
As far as the rest of the house, I think it depends on your threshold for what "needs" to be done. I like order and organization, but I realistically can't do it all. So, I've learned to live with things not exactly like I like them.
Your 4 and 2 year old are probably old enough for simple chores (bring plates to the sink, putting clothes in the laundry basket, etc).
I was wiping down windows a few weekends ago, and mine (same ages) thought it was SO much fun to help me. They didn't really help, but it kept them occupied while I was trying to get things accomplished.
If you can swing it, have you considered having a cleaning service come in once/month to help with some of the larger things that you just may not be able to feasibly get to?
Good luck! Hopefully, it's just pressure you're putting on yourself vs. being an actual issue.