Pain in my right arm after using new mouse, also there's random fasciculations/twitching, and numbness? pitched nerve or worse?

Mild pinched nerve : Your symptoms are likely related to mild pinching of the peripheral nerves in your arm sometimes causing intermittent muscle twitching. This often happens due to the way we sit and either put pressure on the elbows or wrists. You may try either wrist splints or elbow pads for comfort. If your pain is not improving or you have any neck pain or weakness in the hand then please see your doctor