Actually, the changes are C#, A and B bass notes. That would certainly imply a C#m. The problem is that you've shifted the whole tonal center. When you play in C#m, you are actually playing in E major... Your song here is B, with it's relative minor or G#m. You've changed the key for the solo, and I didn't even realize it at first because there are no chords being played there, but if there were, they would be C#m, A, and B.... the thing that makes it a key change is the "A" chord. So.... in reality you need to get rid of the "A" and play something else, and then play in B major, or G# minor.