I'm sorry that you are going through this. It's good to hear that you are trying to stay positive. I know that you are going through a difficult time. But please trust that you can make it through this. Do your self and your son a favor and focus on a beautiful life without him. Throw yourself into your new world. Try and find a place that you can afford alone. Or turn to family and friends that can help you through this rough time. Your ex changed his mind about the relationship you all had. That is sad, but now you need to change yours. Don't tell yourself that you can't go on without him because the truth is that YOU CAN. Perhaps you have been in different relationships in the past that ended and you made it through. You made an important decision that will change your life and the life of your son. Focus on the new you and new beginnings. Though it seems the relationship is ending sourly, try and be appreciative of the good times and the valuable lessons you gained and don't give too much energy to mourning the loss of it.
I will be praying for you and the little one.
Hang in there and keep your head up!