I am 45, single, never married and no kids. I am also very happy. I do like dating but have not found someone who would make me happier being with them than I am a single guy. I certainly would not likely know if she was that right person after only a few months of dating.
Do you enjoy his company? Is it your fear of being alone that is driving this or is it really about the relationship. Not knowing either you or the guy it si tough to say, but at this point in your life after having raised a family, is it more valuable to have someone with whom you can share daily activities and special moments (like you have right now) or is it about 'moving in together/marriage" even at the risk of losing what is apparently making you happy.
When/If the right gal comes into my life, I certainly will not be jumping into having her move in or marriage.
My 2 cents