I need to know why

Why when I eat junk food like pretzels and sandwhiches does my urine ph go to over 8?

Yet when I eat alkaline foods like veggies all day it stays low?

I can't eat sandwiches an junkfood obviously it's bad. And acidic, I can feel my stomach burn after eating these foods.

My doc said cause I'm so malnourished. Which i am, an very underweight no matter how much i try to eat. Im hungry an hour or two after a huge meal. Im always hungry. I think it's me feeding something that's putting off an alkaline waste.

If it matters, blood type AB+

Not long ago I had oatmeal....acidic food. Yet it's been what 2-3 hours now, an ph is 8.