If you have been experiencing lower abdominal pain and have missed your menstruation for 2 months, it is important to first take a pregnancy test to rule out this possibility. If the test is negative, it may be due to factors such as illness, stress, fatigue, or changes in routine. It is recommended to continue taking pregnancy tests every few days until you either get a positive result or your menstruation starts. If your cycle significantly lengthens compared to usual and the tests remain negative, it is advisable to consult a doctor promptly.