I'm 20, I do eat well and exercise quite a bit. I am under quite a bit of stress from my summer chemistry course.
I just got back from the doc, he ran a ton of blood tests, and nothing. He's sending me for an ultrasound, I didn't like his CT idea, not a fan of high radiation. If the ultra shows nothing, I'll ask for an MRI, there's one here in town. I have no idea why they would even use a CT for abdominal stuff, except for cancers. I highly doubt it's cancer, as do they, MRI would make a lot more sense, according to my limited knowledge of such things.
My hands are tingling a lot less. May have just been a compressed nerve or something, like Limes said.
As for B12, I take Deva multivitamins, and I'm fairly certain excess B12 is excreted through urine anyway, I'd have to take a heck of a lot to overdose on it.