Q: "do you think he is pulling away or needs time to think about things?"
A: He could have pulled away if that was his intent without telling you that he needs time. It is possible that what he had told you reflects his intent and state of mind. If both of you felt that things were going well, then it may be that he felt a bit scared not knowing what the future will hold, wants to slow it down in order not to sabotage what could happen with the relationship, etc. He may be using this time to reflect on his life even though he had lived a single life for 5 years, it does not mean that he wants to remain single. He's also not in his early 20's when bachelorhood offers more possibilities; he's at a mature age now that may be thinking about his future with a partner.
The two of you have to be clear on what taking things slow mean to each of you. What it means to him may not be the same to you. As long as both of you are openly communicating, you'd be less anxious and won't have to guess what he wants.
Hi Dr. Rossi,
I have a question for you. Should I wait to hear back from him a little longer or would it be acceptable to call him in a few days to find out what he's thinking about? I guess I need closure?