L.D.
Hi! I am very regular (like a clock) and have had this happen to me sporadically during my cycle a few times in the past. It depends on when during your cycle this is occuring (I usually can tell, because of my regularity).
It could be the result of ovulation - after you ovulate, estrogen plumets and progesterone sores - if this change is dramatic or happens quickly, it could result in some spotting mid-cycle. Spotting like this can also happen before your period begins - the shrinking of the corpus luteum ends the production of progesterone, which then signals your period to start. If the corpus luteum shrinks very gradually, you can spot before you start a full-on bleed.
However, I've also had this happen when I was pregnant. Implanation bleeding can happen, and generally occurs sometime during the 6-12 day window after ovulation.
The general rule for concern is how long the spotting is going on. Anything more than 3 days warrants a call to your doc. Chances are it's nothing, but since your cycle varies so much, it is probably hard for you to determine if it's ovulation related or not. Your doc should be able to tell you more tomorrow - in the meantime, don't worry too much about it. It very rarely indicates a serious problem.
Hope this helps!
