b-12 shot isn't working

A few months ago I noticed that I was having problems...........horrible mood swings, headaches, being tired all the time, I'm talking falling asleep on the couch and not realizing I am still in my work clothes until the next morning.  I went a hormone specialist.  She took me off my birth control which really helped.  A few months later as a result of a saliva test she put me on B-12 shots once a month and Progesterone.  Well, the B-12 shot worked for about two weeks..........any ideas of why????