midlife
The frustrations of trying to resolve issues hidden in a tangled heap of threads can mean scissors come out, when a more patient unknoting would have done the trick, without any severing required in the process.
Your failings.
Your husband's failings.
The relationship's failings.
Your children's health issues.
All sorts of other stuff.
They are all muddled up together in horrible, tangled mess of "I'm not happy".
Right now it is possible that your crush has required you to employ a "filtered" lens in order to justify your response to it. Which might be making your husband and your relationship appear somewhat more one sidedly lacking, more irredeemable and more "blameworthy" than they really are.
Bin the crush. Give yourself time to properly knock it on the head and reset to normal. And THEN autopsy your relationship.
Once any lens can be considered no longer a risk factor in terms of providing a filtered picture you'll be in a better position to work through untangling and examining issues. Then you can sort them into "shit I'll have to deal with either way", "stuff we can work on", and "deal breakers".
But take care not to skip steps. Start with you and the rather glaringly obvious fly in the ointment you are plonking in the marriage before you start on anybody else's faults/shortcomings.
My son was 2 when I was in a similar situation to you. On top of all the normal life pressures we were dealing with MIL's extreme mental ill health. I was at a really low ebb. I was about as far from a happy bunny as I could be. And I blamed ... DH pretty much. Becuase that was more palatable than picking over the details of my own clay feet. Which I certainly didn't do with the same enthusiasm I employed when poking at his faults. I was pretty sure that what I needed to do was leave him, becuase it was obviously not working for me if I was so unhappy and ... well that couldn't possibly be my fault ! 
DS is 15 now. Our 20 th anniversary has just happened. MIL is dead, but in the last part of her life we got through far far far worse ramifications of her illness than we had ever met previously. Perfect we are not. But we are content most days. And properly happy lives in our house from time to time.
I can't promise you that as an outcome. But I can promise you that if you start first with you, your actions, your choices, your flaws.... you will be in a far better position to work out what ails you and the family. And better placed to evaluate any potential solutions to make things better than they are right now.