Wow.... I am nowhere near you in terms of children numbers and ages (no wonder you're finding this difficult!!), but I can understand how easy it is to just become 'mum'. You kind of lose yourself with young children. Your life is all about them for the first few years.
My advice isn't anything new or groundbreaking, but I think it's so important to get away and spend time on your own and as a couple - no kids around.
If there is any way you can do this, do it. Beg, steal, bribe, borrow friends/relatives/babysitters and make time to go out with your husband for a drink or dinner or whatever.
I when DH and I do this (he is quite firm about this, I have to admit it takes effort because I am always tired/can't be bothered/just want to go to sleep!, but when he does manage to persuade me I feel so much happier afterwards.
It's like we remember why we got together in the first place, and we're not just discussing children the whole time.
Similarly for you on your own, you need adult time or simply alone time to do something you enjoy.
Hobby, going for a walk, or just going to a cafe and reading a book on your own, whatever you need to do, do it.
You'll come home more refreshed and patient and appreciative of things.