Is my teenage son gay?

I am worried about my 18-year-old son who spends all his time in the company of girls. I know few of his male friends, and most of the time it is girls who call him. He has started exhibiting female tendencies, which are worrying. He is often concerned about girly stuff like his nails, hair and appearance. The other boys of his age seem to be more manly. Is there a reason to be concerned about this behaviour?

{Wangu}