What should I do?

There is a guy I know "Shane" that is an Army recruitor. He is about 25. I don't know what to do about how he acts around me.First of all, I am friends with a couple of his other recruitor friends in the office--I bring them all cookies and treats every other week.They call me the cookie lady. Iam a few years older than "shane"--One minute he is standing next to me flirting with me and following me around like a lost puppy--and just being all friendly and chatty with me--then the next time I see "shane" he acts like he cant stand me like I make him sick--he avoids me, he looks at me like he is repulsed by me(someone said its probably because I am quite a bit overweight that me may look at me like that) and he acts like a total jerk. It confuses me because he acts like Dr Jekal and Mr Hyde--I know that some people may say Im stupid to not be able to figure it out on my own.But seriously I just don't know why he acts like that.Some of my friends say to confront him but I am NOT like that