I started riding this past February and experienced pretty severe thumb pain and some wrist pain too. My thumbs were aching most of the time and they were kind of weak...like if I tried to pick up something heavy, it felt like my thumbs would go limp. BUT, the good news is, this has gotten a lot better as I've been riding more. I still have a little thumb/wrist pain but only after 30 miles or so. And it goes away when I'm done riding. Also, I'm on my 3rd pair of gloves. My first pair was too big and didn't have enough padding. My second pair was too tight and had too much padding. Now I've found a pair that's just right. So you may want to check out some different gloves.

Hopefully your thumb and wrist pain will subside at least somewhat. I was getting really worried about it, and then it got better. I hope it's the same for you!