J pouch complication? Or is t something I ate?

I’d guess it’s most likely a garden-variety intestinal bug, or perhaps a reaction to the pineapple. In either case it should clear up in another day or three if it isn’t something more complicated. Be very, very careful to stay hydrated: you should be peeing light-colored urine at least a few times per day.

Is anyone else in the house sick?

Could be the pineapple. That’s sent me running before. The oddest and unexpected things can do it and everyone is different. It may even change over time.

I can eat broccoli and Brussels sprouts all day, but forget even a small amount of lettuce, apples or grapes. 

12 weeks out isn’t long. You may be adjusting and it will be a trial and error process with foods.

Thanks for the tips! I feel totally fine otherwise (save for a bit of pain in my lower left side... possibly kidney? Maybe a bit dehydrated?). And no one else is sick. Today is a bit better so far so fingers crossed it will pass and it isn't something warranting a trip to see my surgeon! 

Staying hydrated and resting the pouch definitely can help these things subside faster.

I’ve had odd left side pains and laying on that side with knees bent frequently helps. Suddenly things move through and there’s relief. I’ve also read laying on your left side encourages food to move through your bowels. Weird little things you learn. Hopefully that’s all it is and you find relief soon.