Had my appendix out 18months ago, and am now experiencing the same pain.sharp abdominal pains.anyone know why?

i had my appendix out 18 months ago and the op went fine. But just now, since about 3-4 months ago i have been experiencing almost identical pain as before the op; sharp abdominal pains, nausea and constant tiredness and fatigue. It's starting to affect me in my daily routine. it's not constant, it comes at times when i least expect it the pain differs. sometimes it gets so bad i can't even bring myself to get up. I'm not sure if it has anything to do with my appendicitis. Does anyone have any idea's of the cause? Thank you, Nicole.