If they work for you. You should see improvements in blood levels from them. But not all people do. Cyano is a synthetic product and some people cannot convert it well to active methyl form. Hence many here skip the shots and use methylcobalamin orally instead, daily.

You can try 5mg a day for a couple of months --take on an empty stomach-- and compare how you feel with the injections.

there are various options here--most stores do not sell this locally--
http://www.iherb.com/Search.aspx?kw=methylcobalamin

Just swallow them, as I don't think the under the tongue business really works.

Also if you get a fasting INSULIN test, you will see if you are becoming insulin resistant. An elevated level means your blood sugars are not being absorbed well into the cells...hence the strange feelings, paresthesias. This test can be more predictive than fasting glucose. If your fasting insulin is elevated, then you need to begin supplements that improve insulin activity and change your diet somewhat.

B12, magnesium, and Vit D are typically common deficiencies in this country. Take care of those 3 and see how you feel then. Acid lowering drugs not only affect B12 absorption.
They also reduce calcium, magnesium, zinc, B12, folate and iron. Those are the only ones proven so far, but other things may be affected as well.

People who malabsorb nutrients may have gluten intolerance. Some people with MS type symptoms have been on the boards, and have improved with going gluten free. Our Gluten board here has many references in the stickeys...places to go to learn about the testing, and neurological symptoms that may point to gluten intolerance. Chronic GERD also may signal this problem. Your need for acid reducing drugs is problematic and may be a sign of it.