Period two months late

Hi! Was wondering if anyone could help me before I spend money and return to the dr. My period is now two months late, when it is always regular. I'm 22 and have never missed a period (besides when I was pregnant)I've  taken hpt and they were all neg. I went to the dr a month ago when I first missed, and they gave me a test which was neg. I plan on going back in a week or two but want some input for the time being. Thank you!