Please try to enjoy the peace. And I'm only kind and patient because I'm so utterly convinced that you do not deserve to be suffering like this. There isn't a shred of doubt in my mind. It sounds like, as an adolescent, you felt mixed-up about sexuality due to your introduction to it being through your discovery of your dad's sex life. While I think it's perfectly fine and healthy to have a non-sexual relationship with a girlfriend (and I do not want to blame her in any way for not pursuing one - it's her choice), not having had a sexual relationship - or at least, having only had a limited sexual relationship - has probably meant you haven't had much of a chance to experience sex in a happy or healthy way. You feel a lot of shame and anxiety and the more you feel these emotions, the more you hard-wire them into your brain. You believe these emotions must be justified (otherwise, why would you be feeling them?), they must be deserved and so you start searching your memories and mentally exaggerating them, changing them, and putting the worst possible slant on them. You're not being fair to yourself. If you're damned for your behaviour, the frankly, you're damned alongside 50% of other men, at least.
You aren't a paedophile. You are a child molester. You've never interacted sexually with a child. By the sounds of it, you've never made someone sexually uncomfortable, shared sexual images of someone without their consent, or behaved in a sexually inappropriate manner towards anyone. You're a good person. Please believe me.