I have a sharp pain in my stomach and I don't have an appendix and they have tacken out a tumor out once befor what could be the cause?

Adhesions? Call MD. Any surgery in the abdomen or pelvis can cause internal scars (adhesions). If bowel gets caught or kinked, can cause partial or complete bowel obstruction-painful. Other possibilities can include internal hernia, telescoping bowel (intussusception), recurrent tumor (don't know what type it was), ulcer, poor blood flow. Could be unrelated and just be gas, call your doc now.
See a doctor. If you have had an abdominal mass before, you should see a doctor for evaluation, especially if you are now having sharp pains.