When you say you have gay fantasies of certain dudes, what is your definition of gay? Like does it involve full on anal penetration or are you just doing some heavy petting, groping or maybe some stroking or sucking etc?
I ask because even married straight guys can have an occasional gay sex fantasy, they may even have them frequently and it's usually about a particular dude who they just have much admiration, respect and brotherly love for. Some dudes even go as far as acting on that fantasy while others may try to talk it out with their spouse and in some cases with the dude who they are fantasizing about. This is actually quite normal and very common.
Although you may not be married being so young yet, I use these examples to highlight that it's normal, common and probably not just a phase.
I personally have many hyper masculine, "straight", married friends who are very anti-gay anything who, behind closed doors and with enough alcohol, will suck each other off, stroke each other and still get together basically for circle jerks. These dudes are in their late twenties to mid-thirties. If you were to confront them on it and even hint that they are not straight for doing that, they would first ask you what you're talking about, would be in complete denial anything ever went down and if you pushed the issue, they'd probably beat the crap out of you.
Again just to further the point of how common and normal it is for even "straight" dudes to mess around is why I bring those examples to light.
If you have a good relationship with your dad, do you think there could ever be any point where you could talk to him about these things? For example, maybe start off the discussion with, "dad I know you say you don't want a gay son, and trust me I like chicks just as much as the next guy, but I am having some unexpected thoughts and feelings that are kinda messing with my head. I have no idea where they came from and what they mean, have you ever had any thoughts like these?"
If your dad was a respectable man and wanted to be a good father to his son, even if he never had any of those thoughts or feelings, he would at least listen and offer some kind of guidance. Not knowing more about you or your father it may sound presumptuous, but I suspect he could share some of his own experiences that would relate to yours. You may be quite surprised to find out he may have had some of those same thoughts and feelings himself. It would explain why he would make comments like "he doesn't want a gay son." Probably because he may have went through the same thing you're going through and his solution was to run in fear from it and try to forget about it and become anti-gay.
How I see it, doing things like messing around with a dude doesn't make you gay, or even bi. But it also means you're just not entirely straight. You'll soon discover that pretty much applies to 80-90% of the population both dudes and chicks. Many chicks will have fantasies of wanting to be with other chicks and many of them will act on it, yet they still consider themselves straight, still staying with their boyfriends or husbands. It's part of being a normal healthy human.
To drive it home, the experiences I've had with dudes have only served to strengthen our brotherly bond and deepen our friendships to something more meaningful and heartfelt. There is a level of trust and respect you build when you share something extremely personal like that with one of your close buddies that surpasses any passing notion of merely coming out of the closet as gay.
At some point down the road if you do find yourself more attracted to dudes than chicks and you find having a romantic relationship with a dude more appealing and gratifying than being with a girl, then maybe you are gay, but until then, I just wouldn't be so quick to judge any feelings or thoughts as just an automatic "yep, I'm gay" proclamation. It should not be such a huge life-altering declaration as many people make it out to be.
Take it slow, get to know people for who they are and reflect on those feelings as you go about your life and daily interaction with people before coming to whatever realization you may settle on. Ultimately, the friendships and relationships we have with people in our lives is what life should be about and they far outweigh any selfish notion of trying to decide your sexual orientation. Don't think of it as hiding some dark secret, you're simply sorting out some feelings and experiencing life, so go get more people in your life to take that journey with.
