It sounds like this relationship has promise but lacks some communication. You have to be able to communicate well as a couple to have a successful relationship. My favorite resource on this subject is the Mars and Venus series. You can learn on your own how to communicate and then teach him. These skills will benefit both of you. The other necessity if you are to live together is to be honest about what you are feeling. This will eliminate this guess work when you think something has changed or what you call "cold". Get to a place where you can bring this to his attention immediately. Learn how to not be angry because you are discussing a tone or a feeling. The more you can just immediately ask each other about fears that you have the more you learn to resolve things before they become a real problem.
You have the physical attraction. Now it is time to develop an emotional connection. Do this by schooling each other on ways to communicate. You can use the methods in Mars and Venus to try out on him and see if this helps improve your conversations. Then decide if you are ready for a move.
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