The excessive fluid in pouch of douglas is suggestive of inflammation. I would advice you two things -
1) Severe anemia
itself causes menstrual irregularity.Try to raise your Hb% with proper nutrition,supplemented by vitamins/iron tonics as per cause/type of anemia.
2) Investigations like Complete blood count
, Mx test- to diagnose infection,
- A complete hormonal
assay for abnormality in hormoal mbalance, if any
- An ovulation study after clomiphene
citrate pills to note Ovulation status.
You should consult a gynecologist/endocrinologist
for getting diagnosed,treated as per need.