It may be, and most likely is your diet. When you say "sick," define this. Are you wiped out? Sneezing, coughing, sore throat?
Are you taking any vitamins, zinlc, fish oil, vitamin C and E?
Do you eat junk food? How much? Are you bulking? What kind of foods are you bulking with? Dieting? What's your macro intake?
Juicing? Oral steroids? Are you taking a liver support? Drinking enough water?
Tons of questions. Now, answer!