What a difficult place to be in. I think one way of understanding this is that you are both confused about the level of commitment needed to sustain the relationship. It also seems that the two of you may not be able to deal effectively with communicating these truths. If a child were not involved you would be able to deal with this by simply moving on, but the truth is the two of you will have to communicate over your child whether you are together or not.
I would strongly suggest a couples counselor because there are a great many unresolved feelings that need to be identified and dealt with. This will help you not only if you decide to stay together, but also if you decide to separate and continue making decisions for your child.
If she is unwilling to enter couples therapy I would suggest you begin individual therapy to sort through the issues evoked by all of this.