On the verge of losing it

Kyle has been ornery since April. Before April he was 95% happy. Now every time we sit down to eat a meal he screams. For an hour. No Mommy! No Mommy! This is breakfast:

Me (as pleasantly as possible): "Kyle, should we go have some food?"
Kyle: Yeah!
Then I carry him to his chair and it starts. "No Mommy! No Mommy!"
I strap him and show him a banana. He says "Yeah!"
I start to cut the banana on his tray. "No Mommy! No Mommy!"
He throws it off the tray. I pick it up.
I show him a box of cereal. "Want this buddy?"
"Yeah!"
I walk toward him, box in hand.
"No Mommy! No Mommy!"
Repeat with three boxes.
Dump whatever the last box was despite protests.
Kyle: "Ba ba!"
I show him a number of sippy cups before he settles on one.
I get the milk out, he shouts, "Yeah!"
I bring him the cup.
"No Mommy! No Mommy!"
He throws it on the floor.
I get frustrated. "What do you want bud?"
"I need a cracker!"

So this happens at every meal for once. We don't always give in to the graham cracker asking, but we do before bed because we don't want to send him to bed hungry. Kyle has always been a perfect eater. He even tries all new things, just refuses them after the first bite.

I called the doctor to complain about this only eating graham cracker stuff. The nurse told me to try withholding graham crackers. Um, gee, she obviously went to school to come up with that answer. I think he has acid reflux. He did as an infant terribly. He freaks out about eating lately, and that used to be his favorite thing. So he has an appointment tomorrow, because if we don't figure this out I will lose my sanity. After three months of yelling at every meal (and withholding graham crackers), I hope we get some answers tomorrow.