I had my first sexual encounters as a young boy, with other boys. But that was before puberty really started, and as soon as that hit I was totally into girls and their asses Just like you, ever since I can remember I was totally into anal (my full story is on the board here somewhere if you're interested). I think some of us are just born with a natural anal obsession/fetish (whatever you wanna call it) and if you are like that it's only natural to want to involve that area into your sex life. It's totally normal and I encourage anyone to try it, male or female, because it's fun and very pleasurable.
Now, there are two things:
1. In our society anal sex is heavily associated with homosexual men. That is just a stereotype that has nothing to do with reality. Do some research, anal play is very common with heterosexual people, people use it in masturbation, also lesbians do it. On the other hand, there are many gay men who don't do anal. What I'm saying: If you're into anal, that has absolutely nothing to do with you being gay. I would describe myself as ~70%straight 30% gay, if you think about it as a spectrum. I'm not turned on by male energy or male attributes. I'm mostly attracted by femininity and I wouldn't seek out a man for sex but if my girlfriend would want a threesome with another man I would be totally fine with that. Shemale too of course, femininity with male sex organs - what's not to like I also like the thought of giving oral sex to a man/shemale.
--> But here's a question for you: Would you be able to fall in love with a man? You know, be in a relationship with him, cuddle in the cinema, kissing, holding hands? Or is it just a sexual thing?
2. Porn is very addicting and it's common to turn to more "extreme" scenes to give you the same kick. I was heavily addicted to porn for a long time and only recently (2 years ago) stopped watching it, so I know exactly what I'm talking about. I watched and got turned on by many many things that I would never ever want to do in real life. But your brain kinda gets accustomed to it when you watch it every day, multiple times a day.
--> That doesn't mean that your sexuality is changing! It's just an indicator that you are addicted to porn.
So, first of all, I would encourage you to reduce your porn consumption, because without "porn-brain", sex is much more intense and pleasurable. And it will help you find out who you really are sexually, you'll be less distracted with porn acts - which are not real. Instead you'll have more space to explore your own fantasies. If it turns out you are "more gay" than you thought, that's totally fine, gives you more options, I guess
I personally have found out that I have a submissive side when it comes to sex (I don't always have to be in that role though), I enjoy giving pleasure and being told what to do sometimes. After years of porn/orgasm addiction, I really enjoy sex that is not just about me and chasing my orgasm. And I have found an amazing woman who enjoys exploring with me, we already bought a strapon for her to use on me
Wish you all the best!
But I don't think porn can turn anything into something they aren't all along. I wondered if I was Gay until I had gay sex. Then I learned that I was 100% straight, without a hint of bi. Our brains can do weird things to our self image. Besides, there's a reason gays have so much anal sex, it feels nice