Help with Major Scale Please

I am writing a song using the chords C,Am,F,G. Do I use the C Major scale for the solo? My solo is arpeggio style and it is within the C major scale. But it doesn't sound musical when I put it all together. Am I forgeting something? What else can I do?
What am I doing wrong?

You need to remember that notes in an F chord are all in the C scale but not all the notes in a C scale are in an F scale. You need to be aware that B’s are flat in F scales and F’s are sharp in G scales. If you are playing them natural, they could be throwing off your whole piece. Try these things and ask again if you have more problems.

What do you mean by playing them natural?

Disregard the question. I completely understand now. Thanks so much.

:-)