Is a weak liver one of the reasons for diabetes?

Hi I am 25yr male. I have frequent skin problems. My immunity sucks. Recently I had a blood sugar level test done and it was bit higher than normal. I am a vegan all my life. I would like to know if a liver problem is the reason behind everything. My doctors thrash any possibility saying that I am too concerned for my age. I m underweight too. Help me here...thanks in advance