Oh, and about the 'using notes from the scale', I've seen pieces that are in a certain key yet use notes outside of that key. How are you then playing in that key if you don't use those notes? How can you actually know what key you're playing in?
Thank you again, you all have been very helpful! 
-Dwpiano
Actually as time goes on in classical music. (From classical to romantic to late romantic), there is progressively more stepping out of key. Listen to late romantic music - especially rachmaninoff and Scriabin. They are perfect examples of composers whose music is still very beautiful but are rich in harmonies, (they step out of the home key so much its hard to even hear the original key in some pieces).
For you: It is a bundle of experience and experimenting that leads to using notes outside of the scale. I am currently writing an etude which is in C major. Yet I use many sharps. It has to do with how much dissonance you like. For example a person that doesn't like it all will play F major (F A C) with a C in the right hand. But if you want to step a bit out of key, you might raise the F to an F sharp for an F sharp diminished. This sounds good too, but its all about context. You cant just throw that in there. You have to know how to make it flow, which is where the experience and messing around with it comes in. It also works, through minor/major 7ths, 9ths, 11ths,and 13ths. They can be out of key (if im in C major and use a Bb [minor 7th]) youd just have to make it flow. (this is what makes the great composers, so great)
Honestly, A very good piece for understanding this is Rachmaninoff's Etude Tableaux Op. 33 No. 2.
Its in C major yet look how much he steps out of key.
I would highly suggest listening to a crapload of classical music and playing a of other peoples music to write better yourself.
I used to write a lot of pop music (Not like modern pop, but just like piano pieces that had horrible harmonies [stayed in key, used chords in regular positions] like yanni and such) and then i started listening to classical music alllllllll the time, and started playing a lot more of other peoples music. When you play others' music, subconsciously your brain remembers the chords and how to use them, so that when it comes time for you to write, you will know how to use it. (dont expect to play the chord once and then use it in all your pieces..it takes time and practice) Even now, Ive gotten to the point where when i listen to a piece and I hear an amazing chord, I print out the music and just play that one chord to see what it was.
But- if you really want to be a good composer, it all comes down to listening a lot (and i dont mean like listen when doing work. I mean sitting down with your laptop in your lap and doing nothing but listening),Playing a lot (analyze the chords your playing - which i see you already do) and just MESSING AROUND a lot. Try out new things. Expiriment. Be very very very creative, because thats where brilliance is.
Remember: not many of the pieces that composers wrote came down by "divine inspiration." Beethoven was said to play hours upon hours aday of just improvisation, and if he'd find something he liked, he'd work on that. And that was Beethoven!
Again, I hoped this helped. : )