I'm a relatively new cyclist (started about 4 months ago). Lately, I've noticed that I have numbness and tension/pain in my left hand (but not my right one) throughout my ride. Every 15-20 minutes or so I have to take my left hand off the bike and stretch my fingers a bit. I feel like there is some kind of imbalance in the way I ride, but I can't pinpoint what it is or how to correct it. Can anyone suggest things I can do to try to fix this?
In case it's relevant, here's some random info on my riding. I'm not doing super-long distances or anything -- I ride about 10 miles 4 days a week and maybe 30 miles once a week (and this is near Houston, so there are no hills). I've been riding a Specialized Secteur Sport which was fitted for me at my LBS (though this was not a very intense fitting -- it took maybe 15-20 minutes).