I had a incarcerated umbilical hernia 2 days ago and now my abdomen hurts whenever I move and I am very tired. What can that be?

Go to ER. If you are already in the hospital and had surgery ; then it is good and this is Post Op pain. Otherwise it is high time to go and seek the immediate medical /Surgical Treatment.
Go to ER Immediately. You had gangrenous bowel and leakage. You have peritonitis and could die.