It is tough to go through loving someone when they pull at your heartstrings, hurt you, yet it is hard to stop the cycle. We all have a need for physical and emotional intimacy, however, in this case it would be best to stop sleeping with him. It will just keep you connected to him on a deeper level and keep you in an emotionally unhealthy spot.
If you cut the physical relationship, you will not be giving more to him than you are getting back. I think it will hurt you less. In the meantime try to focus on something that is exciting that you can look forward to that has nothing to do with him. For example, do you want to take a vacation somewhere? Do you want to change your look? Do you want to learn new things? It might sound funny, but being excited about something you always wanted to try and carrying it out will give you a dose of happiness and a new outlook that will be good for your well-being. You can involve your child as well in your new interest.
Romantic relationships are only one aspect of life. When they aren't going the right way, it is always good to look for another aspect of life that can bring you joy.