Why are my vitamin and mineral counts so low despite supplements

I had all but 8" of my colon removed in May 09,I became infrcte4d with MRSA,Blood Poisoning,and Bacteria Fragillis(sp?)I also have hypo gamma globulanemia,and my question is,do either of these conditions cause me to have very lowCalcium,B vitamins, Vitamin D,Vitamin D3,Magnesium,Potassium,and ferrous levels,despite the fact that I take a multi-vitamin-mineral,and supplements for all the above.Is there something else that could be causing these consistant readings such as Post Menopause,or something else?
                                               Thankyou so much for your time,thoughts,and opinions,they have been a great help tp me in the past.
                                         AquariusAudrey