Hi Paffette, I'm sorry to read that you are struggling and disgusted with your doctor for his/her offhand treatment of you.
Firstly, it is not uncommon for some symptoms to appear to be getting worse before they get better. In a perverse way this is a "good sign" that the B12 you are having injected is starting to repair the damage caused by the deficiency.
Secondly, as Jazzyanne mentioned you need a healthy level of Folate (folic acid) as this is essential to process the B12 you are having injected. Check with your doctor to see if this was tested for.
Thirdly you should be being treated in accordance with the BNF guidelines as below. Sadly doctors tend only to read the first paragraph and not the one I have highlighted in bold italics.
Treatment of cobalamin deficiency
Current clinical practice within the U.K is to treat cobalamin deficiency with hydroxocobalamin in the intramuscular form outlined in the British National Formulary, BNF,
Standard initial therapy for patients without neurological involvement is 1000 μg intramuscularly (i.m.) three times a week for two weeks.
The BNF advises that for Pernicious anaemia and other macrocytic anaemias patients presenting with neurological symptoms should receive 1000 μg i.m. on alternative days until there is no further improvement.
However, the GWG recommends a pragmatic approach in patients with neurological symptoms by reviewing the need for continuation of alternative day therapy after three weeks of treatment.
I suggest you make a list of your neurological symptoms and present them to your doctor. If possible take someone with you who can verify your symptoms as the doctor is less likely to pooh pooh you in front of a witness.
You are entitled to ask for injections evey other day until there is no further improvement and only you will know when this will be - not your doctor.
If you have any further questions please don't hesitate to come back on here but be assured thare is life after P.A. as I have had it for 45 years and I'm still "clivealive" at the age of 75.
I wish you well