if someone is like that he could have had a bad history and wanna do things differently an epiphany if you will or he has some serious "performance" issues.
what i don't get is the fact you have kissed each other before but now all of a sudden he doesn't even do that. So this wouldn't fall into the performance category but more in the bad history category. It does seem logical for someone with a bad history seeing the same thing happening again making a drastic turn around.
Kinda like a person that is never assertive but suddenly changes his lifestyle and therefore becomes too assertive cause the person doesn't really know how to balance it since he never experienced being assertive.
As I understand this has been going on for a few months now. So it might be time to do some serious talking. Have a relax evening at home with maybe a dinner and a movie, maybe some wine etc and afterwards have the talk. A serious talk where you get deeper into the conversation and get to know him better.
As i understand you already talked to him about this and he gave you some answers. Well let him elaborate on that, let him talk about what really has happened in the past, maybe it sounds logical on why hes doing this now. I think after a few months you deserve to know a bit more about the man and why he does or does not do certain things. You setting the mood by telling stuff about yourself helps to. I find it easier to talk when both parties are opening up to each other and basically both persons are showing their vulnerability.
if the answers aren't satisfactory or he is trying to avoid the questions setting ultimatums might be a good idea but in my personal view ultimatums suck cause i don't like to be told what to do. So you will have to determine for yourself what kind of person he is.