Changing your mouse is sort of like applying a band-aid when a tourniquet is needed. The tendons that are used to move your wrist go through little sheaths when they move. Repeated use can inflame the tendons and make them rub up against that sheath rather than gliding through it. You need to get that inflammation down. Changing to a different mouse may sort of help by altering angles in your wrist, but not much since they all have the same basic design.

You should consider one of those wrist rest mouse pads and taking some NSAIDs. Or learn to use a trackball.

I'd start by using a very lightweight wired mouse all the time. A couple of years ago I was already feeling some numbness in my wrists from using a standard shaped keyboard and the Logitech MX1000 mouse.

I switched to the Microsoft Natural Keyboard 4000 and the Logitech MX518, both ergo models and the mouse in particular very very light and easy to move around with a moderately high DPI. I'm 99% cured from that numbness I was feeling and I still spend hours using the computer every single day of the week.

I have recently replaced the MX518 for a G5 but the former was a bit lighter so I'd not hesitate going with that