Hi,
I don't tend to hang out on the forums but thought I'd chip in on this thread as it sort of called out to me.
Firstly, I'm married to a woman, but when I was single and in my youth I had a number of encounters where I have interacted with men. This started out in my teens by having a best friend who we shared a porn mag with. We used to call each other and ask for the mag to be left somewhere to be picked up by the other to 'use' when the need arose.
One day, we were both together and his house and parents were out somewhere and it just happened. I won't go into it because that bit is more detail than is needed for this message.
We carried on like that pretty much until we were both able to get ourselves girlfriends. Ultimately we were both attracted to women, but were relaxed to help each other out (so to speak). He's married as well now and has kids, not sure where his head is as I've not spoken to him about what happened since.
Later I went on a very very long stretch where women were my everything - I LOVE women! Then one of them used her vibrator on me and it re-awakened long idle thoughts of what had happened when I was with my mate. It took me ages of sitting and wondering if my experiences with him and then a girl using a vibrator on me made me 'Gay'?
Later in my late 30's I had a few interactions with men, where it's simply been about pleasure - but not for one second did feelings come into it. No kisses, no cuddles, none of that.
At 46 years old I have come to the conclusion that maybe "Gay" and "Straight" are actually labels that we use to assign what kind of relationships we want. If you're gay, you're attracted to same sex individuals, if you're straight you're attracted to the opposite sex.
This leaves a bit of a void that I, as a man and maybe many other men and women fit into - which is, what are you if you're emotionally 100% tuned to the opposite sex and thus "Straight" but enjoy the sexual touch and interaction with the same sex? - I'm not even sure "bi" is the right stamp, because for me it's "situation" based, I'm as likely to say no to someone as I am to say yes!
But when it comes to needing to love and be loved, I just don't think (speaking from my mind and heart) I could ever be with anyone but a woman.
So there you go, my story and view on this interesting subject.
Edit: To answer the question, No. Not all straight men are bi. But we need to acknowledge the differences between what we seek in an ideal relationship and what we enjoy sexually.