If I'm lucky, I will get one this month. Mine is horribly irregular, changing in flow, duration, and span between every single time. You're quite lucky, really.
Stress, a new diet, depression, exercise, all of these things can change when the red woman shows up. I'd say wait a few more days, then if nothing after that kind of regularity, see a doc.
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Every time you think you've made it idiot proof, someone comes along and invents a better idiot.
?the end of our exploring, will be to arrive where we started, and know the place for the first time. - T.S. Eliot