It takes two things to have a sexuality defined:
1. Desire.
2. Action.
To be straight, gay, or bisexual, you need to both desire the specified gender(s) and have had encounters or actively want encounters.
It sounds like you're just turned on by porn. I had a friend who was disgusted by pedophiles, but enjoyed looking at porn that had children in it. Some people are turned on because it's taboo, not because they want it.