I knew some body who just like you ate a lot,frequently and in between meals.She was by no means overweight.She complained a lot if she skipped a snack,she suffered as if she starved for days if a meal is delayed by 10 minutes she could literally faint.Had no health problems or any thing else.I heard people like her have a condition where the metabolism is on overdrive.What ever you eat gets processed and absorbed very fast.And you are hungry again and crave food frequently,but all that extra food does not lead to extra pounds on your body.I am not a doctor,but have seen a person like this and she was fit and healthy.Her eating was unusual and similar what you have explained.