Slight pain in my right arm and neck after using new mouse(80+ hours), also there's random finger twitching, numbness?

Possibly CTS: Sometimes when there's repetitive up-and-down motions of the wrist there can be irritation of the median nerve. This can be associated with carpal tunnel symptoms (CTS). Some people experience numbness of the fingers (usually the first 3 fingers) and on occasion there can be even be backwards (retrograde ) conduction of the pain up the arm into the shoulder. A wrist pad by the mouse might help.