My elbow hurts because of over mouse useage at work or wrong mouse useage at work, what should I do?

You need to build up the forearm muscles that support the elbow, too. I had tendonitis in both elbows and found this exercise helpful:
Tie a string around a full soup can (I used Progresso because I'm tough). The string should be long enough to hold the end straight in front of you when the can's on the floor. Leave some extra for tying around a stick or dowel. Wind the can up to the stick with both hands, release, repeat. It will kill you at first. Then you will gain superhuman powers.

I never did any stretches.

Wow I am amazed at all the wonderful suggestions here. You folks have surpassed my wildest optimistic expexctations. "Take the arms off your desk chair" is actually freaking on the money and I wouldn't have thought of it. I also admit to resting my elbow on the desk! Whoops!

The ergonomics people are coming to inspect my workstation in a week's time. In the meantime I've made a doc appt I don't really want to keep. It hurts more at home but at least I've figured out how to make a proper sling by myself now with a sheet. Also using a mouse with left hand is weird - all of a sudden left click is right click and vice versa. It's a learning process.

I gave up playing bass for the time being.

To answer the question upthread, the part that hurts is the part that faces the sky just about one or two millimeters from the inside of my elbow bone if I bring my hand to my shoulder. I think it's supposed to be "tennis elbow".

But thanks for all the suggestions, I will analyze them in greater detail when I am no longer drunk.

Quite sincerely, Cheers.

Your off hand will not be so deft as your dominant hand, but you should be able to perform adequate mousing with it after a very short time. Brains adapt.

I switch my mouse from right to left for a few weeks at a time to divide the strain between left and right. It takes an hour or so to remember again that I'm mousing with my left (or right) and then it's no biggie.

I used to have excruciating tennis elbow from mouse use. It was worst at night; would keep me up all night sometimes. Also sleeping with my arm at my side instead of up over my head has helped.

Believe it or not, push-ups can also help. Also there is a yoga stretch that is good that is not on that stretches page, where you put your hands behind your back in a praying position.

just try being less of a pussy first

wtf try being less of a bitch

No no no no no, the proper response is "I'll be less of a pussy when you're less of a dick. Which is never. And I believe we're all the better for it!"

That's really weak Bimble. Tony Wilson would be ashamed of you...