There is always a chance of reconnecting with a past love especially if they share a child together and are there for the child they sometimes find themselves falling back in love with each. What I suggest to you is to take things slowly at least until you can find closure in your marriage. It's good that he return the feelings that you have for him it will make it easier to take the relationship to the next level when the time comes to do so but make sure that you can give him your full attention which means leaving your husband and getting rid of any emotional baggage you may have with him.
Couseling is a very good idea but it's important for you to do individual counseling first and then couples counseling later if need be if you do both at the same time it will be overwhelming and time consuming. You will have a much better chance at making it work if you work on your individual issues first and then if you still feel you need couples counseling then consider it after that because individual counseling may help with the trust issues and then you won't need the couples counseling.