I agree with most here that your situation is difficult for us to understand, so I will instead provide a few observations from my life that might be food for thought:
First, if you still have affection for each other, try couples counseling. I learned the hard way that if you leave that too late, things are much less likely to be fixable.
Second, I have lots of friends who have divorced parents. In my observations, my friends whose parents split when they were very young (babies, toddlers, etc.) and then went on to remarry partners who were a better match, grew up to be very happy, well adjusted kids and adults with a good appreciation and understanding of loving relationships.
Third, many of my friends whose parents stayed together "for the kids" but were miserable, totally knew that their parents were unhappy, and have had some related difficulties in their adult relationships.
Finally, I have three (unrelated) friends whose parents split up while we were teenagers. These friends had the hardest time, all three suddenly going from normal, reasonably happy teens to changing dramatically and adopting very risky behaviors. These three friends had the hardest time recovering from the trauma of having their bedrock relationship torn apart in the teenage years.
My takeaway from these observations is that it backs up the common understanding that children need love and stability to most effectively learn how to build adult relationships of their own, and that it is best if that solid foundation of love and stability is settled as early in the child's life as possible, including if that means that step one is being a happily divorced and single parent with a cordial relationship with their child's other parent. The number one thing is safety, stability, and love for the child.
My advice is:
If you believe the relationship is and should be salvageable, seek counseling now. Truly now. Make the appointment tomorrow.
If you decide that it is not, or you go to counseling and realize then that it is over, then try to work out an arrangement with your partner that you can both live with, and get on with it. Once the decision to leave is made, let it be final. It would be torturous and confusing to a child (and to yourselves) to allow the relationship to become on-and-off-again.