Hi Oneday,
How are you doing at the moment?
My first thought is: don't let the guilt get you. That's the beginning of the slippery road.
When you see how many kosher yidden, have, R"L, stumbled into this, it gives you an idea of the toikef of this yetzer hora. I feel like the use of the tools booklet, and the attitudes booklet will be very helpful, but you are very fortunate not to have let it develop into an addiction yet.
I hope you'll find the 90 days easy and that you'll end up having been mostly unaffected by it into adult life.
God Willing, you'll be a beautiful husband and father, at the right time. (I seem to remember the attitude handbook mentioning that even some of the Gedolim had made reference to the sins of their youth).
I guess my point it, you are at a cross roads, between healthy progression, and destructive guilt and depression. I hope that by finding GYE you'll be inspired and empowered, and you won't have to go through the awful experience of fighting this while feeling totally alone.
I wish you all the luck in the world. You inspire me (-:
NGUYOB