If you're 100% straight then why would you let a guy suck on your nipples, and fantasize about sex with guys as described in your other questions?
Anyway, regardless of your motivations, Sam is completely correct. You're just a human being, and humans are a very sexual species of animal (like pretty much every other animal species on the planet). "Straight" and "gay" are nothing more than labels, and like most labels they have a very narrow definition of what they refer to. Humanity is far more complex than what a handful of restrictive labels can describe. So, stop trying to live up to labels and simply be you.
If you want to try various sexual activities with another guy, find someone who wants to do that with you. Ideally he'd be someone who's a best friend so that you two are very comfortable with each other and very open in the things you talk about and let each other know about yourselves. If you don't have a good close friend like that who is interested in sharing sexual fun with you, turn to a friend who is perhaps bisexual or gay and open up to him about your curiosity.
In the end you may decide that same-sex sexual activity just isn't for you, or you may find you love it, but in either case you would at least know the answer to the questions your curious mind is wondering. If you do decide to go forward with sexual activity with someone (of either sex), just be safe and smart about it by either using protection or by both of you getting a thorough STD screening to know for a fact that unprotected sex will be safe.