Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...

B-12 is an energy vitamin. You would probably be feeling a burst of extra energy from the shots. Mine only lasted about 2 days of more energy.
I take 1500 mcgs orally each day now. (Micrograms, not milligrams). No more shots.
BUT, make sure all of this is done under a doctor's supervision. You can get TOO much B-12 and that is BAD. Even when I was taking the vitamin B-12 pills, I was taking 3000 mcgs a day, and it showed up on a blood test that I had way too much B-12 in my system. So my doctor had me cut it to 1500 mcgs a day, which seems to be okay for now.
Please check with your doctor and do this under their supervision. Too many people take supplements and don't realize the possible dangers, Not saying YOU, but I have read stuff on here of people taking vitamins and supplements with no idea what they are doing. Again, not you.