I'm not going to actually pursue girls even when there are mutual feelings
Why would you not pursue girls even if they like you back?
Because having sex is not safe, especially when you are in a relationship.
Finding the right girl to be intimate with is important and you're right not to take the decision lightly. Don't give up on love, and find the right partner before you decide to take it to the next level in the relationship.
I'm fine with just fapping, I'd rather not risk getting an STD.
You aren't going to get a disease just because you've had sex with someone that you're intimate with. You can both take a test every few months to make sure you're clean, and then you could be free to have sex all that you want with full safety.