Need help with a bike issue



I achieved a milestone this past weekend. 3 years ago, a friend got me started on road cycling; at that time, a 15 mile ride was tough. I worked at it and rode my first metric century. 2 years ago, I rode a few metric centuries and finished a century. Last year, I rode a few centuries. This year, I trained and I completed my first double century (Solvang Double Century) and my goal is to qualify for the CA Triple Crown. I owe a lot to cycling...I lost 35 lbs, lost my pot gut, down to about 12% fat, and I'm fitter than guys 20 years younger than me at work.

I have a dumb(?) question. This past weekend, I completed my first double century ride (Solvang Double Century). During the ride, my bike started leaning to the left. It wasn't due to the wind. I tried adjusting my weight distribution, putting more weight on the right pedal then the left pedal, tried pushing the handlebars with my right arm but nothing worked. The lean was so bad that my left knee was hitting the top tube while I was pedaling. I checked the wheels to make sure they were aligned.

I had my bike professionally fitted at a LBS (BG fit). Any ideas or suggestions? Thanks in advance.
 
I used to ride with a very good racer who would sometimes sit cockeyed on his bike, rotated on the saddle with one knee almost hitting the top tube. His hips were obviously not square to the bike and was the result of a biomechanical issue in his back. You might have a friend observe your position on the bike.

As to mechanical issues with the bike, check your saddle/seat post for rotation, broken or failing saddle rail, seat clamp. Inspect your fork carefully for blade alignment/failure.

Since you were fitted, I would inspect the bike for alignment problems and then return to your fitter. They may have got something wrong or missed something (a shift in position) that showed up due to fatigue during your double century.