Flirting

Guys, Why does my male friend flirt with me but clams up when I ask him about it?

Ok, first I know I'm a little too old for BS but I've been hanging out with my old co worker. We are friends nothing sexual and he flirts with me all the time we hang out. The guy is 5 years younger than I am and we have a blast hanging out together. here lately he has been flirting more and more and when I finally said something he clams up about it. Like for example we went out a few nights ago he would grab my waist from behind twice. Then blew into my hair when we were in line and would tug on my hair as well. I finally said something today when we had dinner I said look I'm not dumb I know you like me. He clams up about it and changes the subject. Then he made the statement that I should get a mini van for when the kids come (I don't have kids). I then proceeded to say to him and who am I gonna have kids with? He smiled and said I don't know maybe a donor. Mind you I've flirted back to test the waters which he seemed to like and didn't say away from (which I told him along time ago I wouldn't reject him). He said he can be flirtatious and a tease but dating me isn't off the table (said that a long time ago). Then he tells me he can be flirtatious. Ok and your point being? I just need a males opinion on this because I don't know which direction to go on this one.

Guys, Why does my male friend flirt with me but clams up when I ask him about it?
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