Mystery Meltdown

A mixed bag today. I sent Nikko off to preschool and everything seemed ok. He came back fine as well, hungry for lunch. The OT wrote on his report:
Singing "Jingle Bells" while jumping on trampoline. Still working on tolerating movement on swing - Nikko doesn't care too much for this - we'll still keep working on it. At table, did puzzles. Does well if hand him 1 piece at a time.

Starting after lunch, Nikko started doing a lot of the Nikko dance. He was jerking around, talking to himself. Audrey was still sleeping and Nikko was diving onto the living room floor, making plastic plates clatter loudly, swimming in plastic food. I had to shush him a few times and wondered if he had too much input during OT. Things died down a bit, Audrey woke up for lunch, then I had to put Ronin down for a nap. The same thing happened later on, around 3:15-ish. Nikko was doing the Nikko dance, diving onto the floor, running back into the kitchen and talking to himself. He'd run to turn on the lights. It was stimming without using his eyes. I was shushing him angrily by now. Ronin got up from his nap in a grumpy mood, of course, but he calmed down in front of The Wiggles. Nikko fell asleep for a long nap, too, and I was really grateful for that. But when he woke up, the best I can describe what followed would be a mystery meltdown. He covered his ears. He cried and whined. He was on the floor pushing me away with his feet, then crying when I got up to walk away from his pushing. He followed me into the kitchen and wouldn't respond to my questions. I tried to give him deep pressure with hugs and strokes but he kept on crying angrily. Ears were covered as if he heard a loud, piercing alarm and couldn't get it to stop ringing. Finally, he signed Pancake and tried to say it, all through his tears and upset demeanor, so I got him a pancake. Then another. Then another. At the end of those three pancakes the crying stopped and he sat in the chair looking worn out. It left me to wonder why he woke up like that, if he was really hurting because of a lout noise or some ringing in his ears. Sensory problem? Swing? I can keep guessing about these things but have no idea what exactly set him off. All I could do later on was load up the dishwasher and then trek out to Walmart for more blueberry pancakes. We have six left in the current bag, but at the rate he was going after them today, I definitely don't want to be empty-handed. I got two bags.