Hi Natasha, welcome to Health care magic forum.
Thanks for calling H.C.M.F.
Your problem appears to be something concerned with lower abdominal organs like urinary bladder
or rectal pathology.If female ovarian cyst(most probable)or uterine pathology may be considered. Ascitis is one of the causes due to any reason like tuberculosis
You may need to have a C.T.scan besides other routine tests for confermation.
I advise you to consult a general surgeon
or gynacologist for diagnosis and treatment. You can consult me for follow up doubts.
Wishing for a quick recovery and thanks for calling.