Irregular periods after being regular all my life

So, I’m almost 26 years old and have ALWAYS had my periods on time according to the every 28 days period calendar. The last few months I have been getting my periods 6+ days late. I’m not on the pill (never have been) I do have unprotected sex with my husband but never get a positive pregnancy test. I get super hormonal like I usually do when I’m PMSing. Just worried this may be a sign of something. I know stress is a factor but I haven’t been seriously stressed in a while. I am a bit overweight but I have been this way practically my entire life and it never effected my periods.. any thoughts?