Just gently OP, I'd suggest that if you find yourself alone you may discover that an awful lot of what is making you miserable isn't down to your DP or your relationship, but the drudgery and sacrifice of being a parent. The loss of dreams, of limitless potential to change our lives, the relentless struggle to balance resources, food, clothing, heating, housing - it can all be crushing, for the best of us.
What's worse is you have a DP who is committed to you, but not challenging you. You don't need to do anything for this secure stable but unsatisfying future to come straight at you.
Perhaps you feel like a rabbit in the headlights? Perhaps you feel you've lost the independent person you were? But it may not be all his fault?
I'd really suggest that you open up about all of this with your partner and tell him you can't commit to the life you have, because you are unhappy and unfulfilled. You can at the very least put things on hold, especially if there is any danger that you might sabotage things.
Then maybe get some counselling to consider what it is that's missing in your life and how and where to find what you need? It may be that couples counselling would help too?
I say this only because someone once said - you only get one shot with the father or mother of your children. You can discover exactly the same issues in a new relationship because you were half the problem.
It seems that your DP is unaware of quite how seriously you need things to change. His drinking and prioritising his social life reflect that he isn't happy either.