I think, like a few others have said, that you need to define what 'your life' actually means. Or more to the point, what's missing?
Seven years ago I was a SAHM. I was thinking of trying to get part time work then my mum was diagnosed with dementia on top of quite a few other health issues. I realised I wasn't going to find a job that worked around DS school day and my mum's appointments (one year she had over 20 individual appointments - no employer was going to give me that sort of time off).
I got very depressed, like you it felt like I was just treading water. I went on like that for a few years - getting very resentful of mum to be honest. DH was very supportive but there was not a lot he could do as he was working full time, other than take over chores to help me when I had an appointment heavy week or if mum was calling to say she was muddled about something. Also, thankfully, he was taking over the care of DS at the weekends just so I could get the down time I needed to save my head exploding!
I started doing some craft things to keep sane and, after a few years of doing pieces for friends, one of them said I should try selling them.
I realised I actually didn't have anything to lose. I wasn't earning anything, so any money coming in was a bonus. I didn't have to weigh a job with the business and I thought I could probably do my work around DS and mum's numerous appointments. And I enjoyed making my items. So I started my own business when my DS was roughly your children's age. Five years later I earn as much from my on-line business as I do from my part time job. When mum went into a home two years ago, I realised I wanted a bit of company as well as a more regular wage, so I got a small job in a local school.
It's not a huge business, DH isn't going to be a man of leisure any time soon but it's my business and I am very proud of it. It has kept me sane because I had a focus when mum's dementia got worse. I did a few day courses to learn more about my craft - DH, again, stepping into the breach to help with both DS and my mum so I could have the day or two for the course.
The thing is that I knew, when I was on maternity leave all those years ago, that I didn't want a full time job again. I didn't want to do the job I had been doing up until then - I'd had a good career but I was bored rigid with my line of work. I knew what I didn't want. I just didn't know what I wanted to do. Fate sort of chucked my business at me.
In some respects you have an ideal situation. I know, that sounds a horrible thing to say given what you've said you feel like. But bear with me. You sound like I was, feeling like I was shouting from behind a muffling piece of glass. But the one thing you have is the knowledge of what you don't want - you don't want things to stay the same - and you have time to work at changing it.
So what would your ideal life look like? Assume you could get child care, move or whatever - all those things are just stuff to be overcome, they shouldn't hold your dreams back. Think about solutions when you know what your barriers are, don't put the barriers down yourself.
What would you see yourself doing? Do you want a career change - so could you retrain either with short courses, evening classes, on line or through OU etc whilst you have young children? Do you want to go back to full time work - could you fund after school care for your DC from increased salary and how would school holidays work? Is your type of work something you can do as a business so you have more control over your hours (in theory!) Do you just want time to get to the gym or take up painting or learn car mechanics - in which case DH is going to have to step up to give you some space a few hours a week. Don't dismiss voluntary work either - I did a voluntary job a couple of hours a week which led to the part time job I do now and it gave me purpose.
Spend a bit of time writing down what you want and don't want (that's just as important). Then work out how you can get it, how to overcome the barriers, what do others in your family have to do to help or what you can compromise on for the next year or two until your DC are a bit older and more independent. Just because they're young doesn't mean you can't make a start and build on your foundations later.
And, last bit of advice. Stamp your feet every now and then. If you decide that evening classes are your salvation or Wednesday evening at the gym is your thing, then that is set in stone. If DH can't get home in time then money's there for a baby sitter. It does not get moved - your time is as precious as everyone else's.
DH's dream is that I fulfil my dream of a successful business (he's still hoping for that man of leisure title ha ha!) But that's how it should be - the greatest reward for all the family should be the smile on each others face.