What Causes Delay In Menstruation Other Than Pregnancy?

Hi

I am Rakhi Gupta- age 25, i am virgin. I am not getting my periods after 9 th june. i missed july cycle and august is baout to come still didnt get any periods till now.

i have faced this problem about 4 years ago.. when i didnt get my periods for 3 months i showd to doctor and had some test and sonography n all but nothig was found after that it automaticllly beame regular.

now i again facing the same problem. please help me out. shall i go to the doctor now or wait for one more week.