It's not a bad logo, however, I feel the font you've used/characters you've designed don't look right. For example the width at the top of the S is wider than the two centre points of the curves for the top part of the S.
As for it looking similar to the Sky logo, I wouldn't worry about that because the designs aren't similar enough that it looks like it's been copied, so there's no legal issue and I personally can see the originality in the design. I didn't think of sky whatsoever until Levi brought up the issue.
Well done though, considering you're only 15 this is very good. I've seen work from much older "professionals" that's a lot worse. It's refreshing to see someone who's new to this that doesn't apply drop shadows, glows, inner glows, horribly clashing colours etc
I think to improve it you're going to have to sort the font/characters out and do something more with the brush. I'm going to assume that SK are your initials and that it isn't meant to read ski.