Sounds like he needs to man up a little...............he can not have security and single life at the same time. Based on what you have said, he has pretty much told you that he wants to go and try this and if it does not work out then he will commit to you. Thats pretty selfish............you can not give one thing a whirl and then go back if it is not to your liking.
The reality is you must make the right decisions for you and your child until he decides what he wants to do. Since he has pretty much said he wants to try and make it work with the new girl then you may want to consider moving on. Just because you move on does not mean that you can not make it work later on. The issue is if you hold on and wait you will come to resent him and if you get back together that resentment will prevent you both from working out the relationship.
You have a couple of options. The first is to sit down with him and let him know that while you love him you can not wait for him to decide what he wants. You have a child to think about and your own heart needs time to heal. Explain to him that for now you really do not want to be friends. That you are going to move on, and that should he decide you are what he wants he can give you a call then and if you are still interested you both can move on with the relationship.
This will do a couple things, it will clue him in on the fact that you deserve respect and that he needs to wake up and decide what he wants before he loses the options he now has. The fact is there are a lot of other guys out there that would love to be your man and he knows this. So the longer he fools around the better his chances of losing you. This reality will spur him into action and force him to take a good long look at himself and what he wants.
You on the other hand will have the time to truly mend your heart. Seeing him and being around him will never get you over him. You can go out and find yourself and what you are looking for in life and in a partner. Maybe you will find someone new that sweeps you off your feet.......and maybe he will come back and you all can work it out. But the reality is you can not hold on forever.
Your other option is stay the course and hope for the best. If you choose to go this route you will have to accept that he may take a while to figure out what he wants and it may not be you. The hardest issue with this is the longer he takes the more you will resent what he has done. If you do get back together you may hold this over his head or come to dislike him for what he has done to you. If that happens making a relationship work will be very hard.
If you do get back together counseling is a definitely do thing. In the end this is your choice. But moving on will not harm the choice regardless.........if he really decides he wants to be with you then he will make his intentions known. If not then he did not truly want to get back together regardless. If you decide to move on then you have some hard decisions ahead of you such as how to handle the house, custody of your daughter, child support so he can help support the child as well as other matters like visitation. Once you decide what you want to do.......it is time to sit down and talk with him about how you are going to handle all of these things.