Hello, this is Dr. E. Greetings from New York! I'm so glad you posted your question for me to answer, and I aim to provide you with accurate info.
I think you would respond better to the shots because they are slow release and you don't need to take them every day AND they will be better absorbed because they don't depend on your stomach to produce intrinic factor and don't depend on your terminal ileum to absorb - it all gets absorbed slowly through the tissues.
B12 pills in general don't usually work very well unless they're in high doses and the intestines are more or less intact.
I answered your questions, please re-read my answer - it is dropping because you are not absorbing it properly. You are not getting the correct dosage form for your condition. You need to tell them to give you the shots because the pills aren't working (no surprise because they generally don't work) and they are making you feel sick.