I think I ruined everything, please help!

I have really done something I shouldn't have done. I've got this minor friend, which are one year under age. I met him awhile ago, and even though I am 5 years older we clicked immediately and soon become best friends.
We have slept beside each other several times without anything sexually happening, despite we are very close and touchy with each other (we are both guys). But last week, I do not why I did it, but I ended up putting my hand down his underwear feeling him up. Not for long, but still I feel really bad for doing it. When I woke up the next morning I ended up holding around his waist, I though he was asleep, but he mention for me after the both of us had woke up that I had snuggled against him, holding around his waist.
He did not mention me touching him in inappropriate ways, so I do not really know if he was fast asleep or actually know what I did to him.
And now I feel our friendship is somewhat stained. Of course he is still the same towards me, but still I can't look at him or talk to him without feeling guilt about what I did.
I want to tell him, and be honest, but he is kind of homophobic, and I am afraid of losing him. Some part of me suspect him for being gay, when we talked about me holding around him while sleeping he called it awkward, and said that he would kill himself if he ever turned gay....
So what should I do?
I know what I did was wrong, so please don't tell or lecture me on how wrong I am, I feel terribly already. This underage friend have been everything I ever wanted in a friend, and we have spent time together every day all summer. But right now I do not feel worthy of the friendship, like I do not deserve a so good friend as him after what I did.
Should I tell him, or should I just live with my guilt?
How can I make things right?