Some time back I had similar feelings. It was at a point when I was spiritually weak (I'm not claiming that for you...), often when I saw a boy in RL I had sexual thoughts, and some internet pics even increased them (of course I would never have done anything to any boy).

There were two things that brought my thoughts back: First, I became aware of how displeasing or even hurting it must be for a boy, and that it would just please myself. It came to my mind how innocent and divine creatures boys are. The whole night I cried for the poor boys I had ever thought of in a bad way.
Second, I tried my thoughts to be not *only* about boys in my free time, but I increased my Bible reading and prayer sessions, worked with my PC instead of watching pics, worked outside in the garden, did more sports, etc.

Today I can say, I have never had any sexual thoughts about boys since then. I love boys, but don't lust after them. I want to help and comfort boys, but could honestly not even imagine to do anything bad with them.

Just my experience.