Read and Answer Please (: I really need some opinions!?

Alright, I've been smokin for a while.. Not proud of it, I just like to be high.. I don't do it during the daytime, or if I have something to take care of. I only smoke when I'm absolutely free, and at night. I do nothing bad when I'm high, I just chill and watch a movie, or read a book, or play the game, or hang out with friends. I use eye drops and gum to make it less obvious. But here's my problem. The guilt. I'm a big believer in Karma, and I don't like the negative Karma i'm gettin.. I want to tell my dad I smoke, I betrayed his trust twice about weed already. He FOUND my stash about 4 months ago! But he couldn't believe it was mine and blamed it on my friend, i didn't deny that. Then, his friend wanted me to pee in a cup for him, but I couldn't cause I'm a pothead... So i lied to my dad and told him i smoked once with my friends (2 weeks prior to the drug test) I just want to tell my dad. He's a pothead too. And when I told him I smoked once, he didn't get mad. He was happy I was "honest" with him. Should I just tell him? Catch him on a good day and sit him down and talk to him? Or should I keep it a secret. (lol don't even tell me to quit, cause i'm not :) (important detail.. i'm only 14)