What Causes Soreness, Pain At Lowest Joint On Thumbs, Base Of Hands?

Hello, my name is Ollis. I have worked at General Motors for nineteen years in production. I have soreness and pain at the lowest joint on both thumbs, at the base of my hands. It hurts to grab and hold anything, even when I hit my hand against something. Also, the harder I squeeze using my hands, while specifically applying pressure on the thumbs, the pain increases. For example, It is painful to give a good handshake because it is necessary for the thumbs to engage. I am forty four years old and I am looking for a doctor who can help me fix my issue.