Having a girlfriend does not mean anything. I know this from experience. I am 26 and I have had girlfriends all my life. I just started talking to dudes about a year and a half ago......... Some people use it as a cover up and some people really are just bi....... Also there are a lot of straight guys that would be bi or gay even but are scared to act on their emotions. Trust me i think there is a lot more gay and bi-curios men then you think.....
Trust me, been there done that. I called myself straight, bi, straight acting, had the girlfriends, the whole she-bang.
There are two levels to what you're saying here. One the one hand, the intellectual one, it's probably true that a lot of guys have wondered.
It's also true that guys who want other guys strongly enough, have a tendency inflate that number out of sheer hope, to see things that are not there, to interpret every move a straight guy makes in the best possible way to mean sex. All the while insistently blindering themselves to all the signs that point the other way.
Is that you? We don't know, all we know is taken from your perspective and your opinion. If you're wrong, we're wrong because no one in here is hearing his side of this.
On the other hand,
gay guys have problems with their gayness, they hide, they rationalize, they make excuses, until they get over the societal prohibition against homosexuality. Do you honestly think, that in reality, most straight guys who may have had one or two random curiosities are going to run that emotional gauntlet just for a few random curiosities?
What we also know, is that if you pursue someone in a relationship, straight or gay, you've inserted yourself where you do not belong. You are in control of what you do, and aside from the messy drama that will result from being the other woman, it's not being a stand up guy, it's not ethical.
The girlfriend is not a mannequin who can't be hurt, even if she never finds out you still affect her relationship, why would you do that to someone?
Why would you treat someone in a manner that would really hurt you if the situation was reversed?