Periodic Abdominal Pain During Ovulation, Pain Resurfaces On Stopping Medicines, Ultrasound Showed Water In Pouch Of Douglas, Normal Pap Smear. What Could It Be?

hi i ve been having pains by the left hand side of my abdormain for more than two years and each time i visit the hospital, i will be asked to go for scan. the scan result always reads water in the pouch of douglas. i have taken a lot of antibiotics and some pain drugs given to by different doctors yet the pains comes at intervals. whenever am taking the drugs the pains will go only to surface after sometime. i remember vividly that the pains started with whenever i am on my ovulation . i run my pam smear test every year and is normal. please am confuse because people will tell me is ovarian cyst and all kinds of things