Could Dizziness Be Due To High Sugar Levels?

I am a 49 year old male, I have been going to the doctor about my dissyness, I started going for this about 3 years ago, my doctor said that my sugar was a little high, so I started watching what I eat, I have lost weight, I have not been on diabities medication, he also said that my cholesterol is high, I have not taken medication for that either, also that I have a little high blood pressure, I have been checking and it is about 127/78 , a little nigh but not taking medication for it, still I am not feeling well, I feel with low energy, dessy, like I am going to pass out, and it seems to be getting worse, still my bloodsugar is not high, I checked it this morning and it is 120, last time I eat was last night , I feel ok now, but when I eat something, I start feeling bad again, I am concern that I have something wrong with my digestive system, I am even worry , that I may have some kind of stomach cancer. My doctor keeps telling me that I have border line diabeties , some high blood pressure, and high choresterol, I feel so bad when I eat, that I do not eat much, I have lost weight, I am 175 lbs now, I am 5 7 , also I work the night shift and do not sleep well during the week, most days I only sleep 3 hrs, that makes me feel worse, I used to smoke and drink alcohol, I stopped both, but still not feeling well, I am going for a physical on Tuesday, I want my doctor to screen my for stomach cancer. My email is YYYY@YYYY .