Hello! Hormones have an impact on emotions, and it is hard to manage the changes for both sides at first. Maybe he just has to get used to it, and understand that he needs to adjust his emotional output a little for you. Being in a relationship with a trans person during transition is not easy, but it is possible if both parts commit and put at least some effort in it. Communication is very important.
On the other hand... Maybe transitioning allowed his true personality to come out and you don't like it very much. I'm not saying this is goin to happen, but you should consider it at least a bit, so that you can be ready to leave whenever you feel you are not getting what you need out of this relationship.
You can always PM me if you feel like talking.