Is the only thing you're consuming on your ride a Clif Gel? What about water or a sports type drink? When you take a Gel of any type according to the labels they say to drink a bottle of water. I don't drink a whole bottle but I do down a bottle every hour.

For my pre ride I drink at least a full bottle, stretch then ride. I then rotate a bottle of water and a bottle of Hammer Heed every other hour and throw in Hammer gel/power bars during the ride. For my recovery I drink Hammer Recoverite in a water bottle, refill and drink a second bottle during my ride home. Once I get home I stretch for at least a half hour.

If you're not drinking during your ride or not using a recovery drink I would start looking there.