Since it's not really feasible for him to talk about what happened to him - both because of the fact that no one would believe him and because the ones who experimented on him would kill anyone who knew what they did - I was planning to have him lie and say that he had cancer. My questions are, would a doctor be able to find out that he's lying about his condition?
Also, what kind of cancer would have symptoms that included weakness, tiredness, and often crippling agony?