Appendix? W/ update

Sun stomach ache after eating restaurant hamburger (I ate it too and was fine). Monday hubby ate leftovers (I know, bad idea) lots potty time. Tues, still felt sick but worked. Wed called off, rested all day, pale, stomach pain. Thurs same. Could this be his appendix? Might have to take him to urgent care or hospital if he cooperates? Is this serious? He doesn't doesn't want go right now.

Was a steak hamburger make from steak cooked medium.

Update:

Thanks everyone. He went to the urgent center and they took an xray. His colon is inflamed and they prescribed 2 antibiotics.