I'm 27, I have 3 kids and I've always had my periods between 27-31 days apart. It's now day 41 and i've taken 2 HPT's and both neg. My husband and I always use condoms and none have broken. I don't think I'm pregnant, but can't figure out why I'm so late. My period came on Aug 27, 2010 then on Sept 29, 2010. It was 33 days which put me a couple days late, then I didn't get another one until Nov 6, 2010. It was 38 days between my periods. I started going back to school in August and I've been a little more stressed out trying to take care of my kids and attend college full-time. Could stress make my cycles change? I'm just wondering why my periods keep getting later every month??