I’m sorry you are suffering from HOCD, I was in your shoes when I was your age. This is a very common worry among OCD sufferers.
Remember there is a difference between thoughts and your own reality. A thought popped into your mind, ‘What if I am gay?’
Most people would not give it a second thought and would forget about it, but a person with OCD can jump on this thought & starting obsessively worrying about it so much it starts to feel real. ‘I’m worrying and thinking so much about being gay, it must be because I am.” But I know and you know that you are not.
Feeling aroused while watching lesbian porn also does not mean you are gay. They have done countless studies on human sexuality and arousal. They have found woman even more so than men can get turned on by different sexual content. Arousal does not equal sexual orientation.
Of all my truly gay loved ones, they all knew from a very very early age they were difffent. As did their parents.
This is your OCD. Remember this and focus your life on more positive and fun moments :)