It's quite possible that he does feel this way about you too. Yet, at the same time, with 2 kids in diapers and one still nursing or with a bottle, there's not much that can really be acted upon.
My own three are slightly closer in age range than yours are, not by much so I'm thinking back to that time in my own life as it's about a decade in age difference now. I was going through some health issues when my youngest was about that age. Depression was on the diagnosis table. Turned out to be a neurological illness which is in remission but the isolation I can most definitely relate to.
It's important to not lose sight of the momentous life alterinh changes that you've just experienced.
If your husband's only flaw is that you aren't feeling connected to him it could just be what you yourself are going through and it's worth talking about your fears about the changes to your relationship. He could be oblivious that you feel like you don't matter. If there's more to him in a negative way then it could be symptomatic of a lingering problem between you. Of which it's important to realize your own vulnerabilities.
I would certainly suggest to wait before making any rash life altering decisions. But know you know and recognize the weakspot of your marriage. It's like playing chess, it really is, life that is. Be cautious of any checkmate scenarios.