What Causes Delay In Menstrual Cycle?

I am 26yrs old...married 5months ago...i got menses for the first time in 1999 and thn the 2nd period i got after 6months...later i didnot get periods...whn i consulted doctor she gave krimson 35 for 3months...by using those tablets i got periods..again whn i stopped using same problem araised...after 1yr again i consulted the doctor...that time she asked me to go for scanning...after checking the scanning report she gave me Elogen and she said my ovaries are small in size...i used those tablets for 3months and i started putting on weight..so i stopped using those tablets....now it is about 1.5yrs i didn't get periods...whether i should undergo any test to have regular periods...pls advice...