D.N.
Mine changed about 7 yrs after I had my first, going from very irregular to just a bit off, missing a month or two instead of 5 or 6. Then I got a surprise pregnancy and it went more normal. But then changed again about a year later. Then after my second surprise (we were using BC then) I had my tubes done and now totally normal, every month. When I was going through infertility I learned a lot. Hormones can really change over time and with each major event (pregnancy, menopuase, internal injury to ovaries or what have you). If you are ever not sure of something, always see the doc. It never hurts to ask. If this happens every month and is not just a little spotting, I would definitely ask about it. The doc may want to do an ultrsound just to see what is going on.