Doc told me they believe i'm not absorbing my food as i should. what does this mean & what should be done?

Long discussion: There are multiple possible difficulties people can have with absorbing the nutrients from food. Unfortunately, it's hard for me to comment sensibly because there's no clinical info beyond what you say your doctor told you. "what should be done" here is a detailed discussion with your doctor -- where you ask specifically why s/he made this statement and how best to address this. Be well.