If your 16 female and you feel more attracted to the thought of being a man and having gay sex with men than just having regular straight sex with men what should you do?

If you're sixteen, odds are pretty good that you should spend a couple years thinking about it before you DO anything. That's especially true when you're talking about something as fundamental to most people's perception of you as gender--while it's increasingly possible to come out, safely, as gay when you're young, it's not quite so likely that your parents or friends will receive "I want to be a gay man" with perfect equanimity. Think. Read. Think more. Find internet communities where you can connect with people who feel and think similarly.

Livejournal is one site with thriving gay and transgender (that is, females who want to be male-bodied, males who want to be female-bodied, and a whole array of people in between) communities, and it can be a lot easier to talk openly about this stuff with people who aren't sitting right in front of you.

One good resource for thinking through some of this is Kate Bornstein's My Gender Workbook. It's not exactly cheap, but you can find it on Amazon, and it's for sure worthwhile.

If you can connect with a counselor (think secular, not religious, in most cases) who is supportive, they can also be a very good resource.

So... realistically, especially as young as you are, be careful who you tell. But don't feel as if you have to go it alone. You're not the only one of us out there.
And do remember that safe sex is the only way to go if you want to experiment.