Fluid in the pelvis can be seen in Appendicitis
,Pelvic inflammatory disease
As Appendix was removed ,it shows that fluid in the pelvis is due to Appendicitis,even though not ruptured.
Pain and cramps in the abdomen can be due to infection of gut,adhesions formed due to previous surgery etc.
Get a Plain x ray abdomen in erect posture and ultrasound
abdomen if you still have pain.
Till then,please take Antispasmodic Dicyclomine
and antibiotic Ofloxacin.
If you comeback with reports,i can clarify further
Wish you good health