Before I started eliminating GERD trigger foods, my symptoms usually got worse throughout the day and didn't really correspond to meal times or eating certain foods, but I was typically eating several triggers a day. My symptoms are pretty well-controlled by diet now though.
You've probably already done this, but have you examined your lunch and afternoon snacks to see if you may be eating something that triggers your symptoms? Or perhaps it's a certain activity -- e.g. sitting at a desk all day at work which puts pressure on your stomach? (My symptoms are always worse when sitting, better when standing or walking.)
Diagnoses: GERD, small hiatal hernia, anxiety, allergies
Medications/Treatments: Singulair (allergies), GERD-friendly diet
Note: I suspect my GERD was caused by taking antibiotics for acne. Please be careful about taking antibiotics when not necessary!