Stomach pain for one week. To severe.

Hi, My wife is having stomach pain at lower tummy for one week. She was previously diagnosed with PCOD on the right and she was under medication for 11 months. Currently she is using only APCOD SACHETS for one and half month. Previously she used Femilon. she is having lower tummy for 1 week. Her periods are skipped by 10 days and still not had her periods. She consulted a doctor the other day, the doctor told to check for pregnancy test and the results are negative. Doctor also told to test again after 5days and gave Folvite tablets for 10 days each after lunch. I am writing this because we want to know the reason for her pain and also wether women do have stomach pain during implantation(pregnancy). Her pain occuring randomly all day and pain ranging from mild to severe. Thanks in advance.