Good thing you turned your sensitivity down, because quick jerky movements can lead to Carpal Tunnel Syndrome (CTS) real fast.
Since your fairly new to osu, I know it can be fun and addicting. But I advise you to take long breaks (days worth), or else you're going to regret it.
From the beginning two months when I started, I had similar symptoms like yours; my hand was shaky and it was hard to move it around.
If you don't want CTS, then take those long breaks and stop playing as much (10 hours....)
Your health is what is most important to you, not a game.