Your GP needs to get their bloody finger out & start your B12 loading dose as a matter of urgency, it is negligent for them to do otherwise!!!
They also need to treat the folate etc too
Please have a read of this website ... HERE
On the "useful links page" you will see "Pat Kormics Facebook Support Group"
Please join that group & they will help you understand what is a pretty complicated treatment protocol. B12 works with other vitamins & minerals, so its very important to get the correct balance of Cofactors so that you have the best chance of fully recovering.
Also ask to be tested for the MFTHR gene defect. This means that your body cannot process Folic Acid into Folate as is normal, so treatment with this can be different
Left untreat, or inadequately treat, B12 & Folate deficiency are serious disabling & even deadly conditions (pernicious means deadly) getting the treatment right could well mean you make a full recovery.
Unfortunately too often doctors, including consultants don't have a clue & you end up with inadequate treatment or in too many cases, no treatment at all.
My DD spent years living & going to school with the diarrhoea you describe, fobbed off with IBS - eventually allergies to soy & Cochinael were diagnosed & we already had worked out for ourselves that she was intolerant to a lot of stuff. She got more ill over the years, Anxiety, phobias, body wide pains, constant headaches, raging insomnia, 2 hours was a good night & so much more. She ended up in a wheelchair & that was on a good day.
It took me 7 months, but thanks to info from the group I mention above, I managed to persuade our GP to follow NICE guidelines & trial her on B12 injections & gave her all the cofactors as per the group admin/files instructions. She was sleeping normally after 1 jab & after 18 months of being unable to stand, she walking again after 6 injections.
All of her allergies have gone, no IBS, she doesn't need the FODMAP diet any more, pain is 90% better, headaches gone & so much more.
Her B12 was supposedly in range too, but according to research it was low for a young teen & I knew we had PA in the family.
I also have it, but my treatment is complicated by an adrenal issue I am under investigations for, meaning I can't take the every other day injections that I need as it depletes my potassium too much & low potassium is bad. But the weekly jabs do help somewhat, though thanks to 14 years misdiagnosed, I won't make a full recovery.
Please join the group & demand your GP treats you NOW!!