I live in a small town. I only play a couple of tournaments a year and about two rapid games a week with my teamates. Therefore, playing online should be my primary source of practice, but I find it really hard to focus and calculate when playing online (rapid or even classical). As a result, I play way better on the board than online. Is there something I can do to play better online?
Have you tried setting up a chessboard by the computer and playing the online moves on the board before transmitting them? This may be more difficult with rapid than classical games, but if you find seeing the pieces in 3 dimensions more desirable, it seems like a practical altenative to looking at them in 2 dimensions on the computer screen. When I work on online problems, I set them up on a board before solving them for that reason.
Have a board beside you when playing online. Make all the moves on the board and think/calculate by only looking at the board. If you're playing a standard time control this won't cost you much time on the clock.
If you're asking about blitz/bullet then I unfortunately have no solution for you, though most people tend to be better online in fast time controls.