You may also try chia seeds in your shakes. Some recipes here already call for them. Chia seeds help you feel full longer, although I don't think there's anything wrong with eating a healthy snack in between breakfast and lunch. As for your heartburn, I would see your doctor to find out if you have acid reflux disease. He may recommend an over-the-counter acid reducer like Prilosec OTC (cheaper at Sam's and Costco).
At least you were only 3 days in!
One of the snack recipes - the almond coconut bar (can't remember exact name) uses dates. The recipe comes out to about 1 date per bar.