What Causes The Presence Of Fluid In Pelvic Region?

I was treated for 1b2 cervical cancer lymph node positive having had a radical hysterectomy, chemo and radiotherapy 3 years ago. I ve been suffering with low abdominal pain,bloating and acid reflux for a few weeks. Had urine analysis which was clear of infection and bloods just revealed low iron level. As I am a medical secretary at a GP Surgery one of the GPs advised I have an ultrasound scan of my abdomen and pelvis. The uss showed fluid in my pelvic area. I m due to see my gynae-oncologist in April for my 6 month follow up, but I m scared what this fluid could mean. Any suggestions? Thank you Donna