B12 Deficient

Mommy to Kai

So out of 8 vials of blood work I had done my Dr only found that I'm B12 deficient.. so my question is

1. Could that explain the dizziness and weakness?

2. Can I take that with my prenatal (8mcg) the pill my Dr gave me is 1000mcg once a day.

3. Are there any bad side effects I need to look for?

4. How can I get B12 naturally??