However shit it is, it's better that the actual alternative of having a man who doesn't want to be there, and that's the reality of the choice, had it been yours to make. In your case, it's not a choice between sad and alone and loved up playing happy families.
Fwiw, I made a big decision 20 years ago that changed the course of my life and immediately regretted it (think moving abroad) but it was only as time went on and life filled in around the sadness that I can now look.back and say, yes, I'll always wonder about the other path, but I'm happy with my actual life and don't need to torment myself about it.
So my advice is to tell you that you don't know where this path is going but you have complete control in choosing to only let good things in, deal with the bad, and hope that in 10 years you're in a better place with a happy confident child, who will spoil you every mothers day because they know you gave them a safe and loving home, and you did that.
Make a plan arund the stuff you can control, like promotion or retraining, even if it can't be now and think of the.payoff...happier life, holidays etc. A man should be able to slot into your life like a cherry on top, not be the whole cake. This is just a hard part of life.