Just discovered why I been so tired and dizzy for a long time

Ok, So I just been to the docters recently for a blood test and discovered that I have vitimin deficiency which is odd considering I do eat a lot of vitimins. I had been in a lot of pain and headaches and got sinusitis for months and now I am glad I found an explanation. The problem is that I am pretty sure I do eat enough vitimins and it seems my body isn't absorbing enough nutrients. I worry that my stomach had been damaged or something because I used to get bloated a lot with horrible stomach cramps and a bit of diarrhoea. I used to feel nausea also. These symptoms I have had been ruining my life for a long time and it frustrates me that I don't know what has caused me to be deficient.