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Heather Corinna replies:
I'm a week late for my period, a little tired, but other than that I'm fine. I've been having sex for a little while but my period has always come between the 17-20. It's now the 28th. I already took a test a few days ago and it was negative. I'm really worried. Please does anyone have answers?
It'd actually be pretty atypical for a regular period to fall on the same numeric dates for a long time, and let me explain to you why.
The number of days in each calendar month is not the same: it varies from month to month. Menstrual cycles, on the other hand, when they're regular, are a given number of days, and months are (sparing February) a number of days longer than many women's menstrual cycles. So, it's pretty much going to be a given that unless your cycles are actually irregular, they're not going to fall on the same or similar dates each month for more than a couple months at a time, and it's also likely that at least once a year, you'll probably have a period twice in a given month.
To show you what I mean, let's say you have the most average menstrual cycle, which is a period every 28 days.
Starting with January of this year, if you got your period on the 17th that month, the remaining months, with a 28-day cycle, would have your period appearing on: February 14th, March 14th, April 11th, May 9th, June 6th, July 4th, August 1st, and August 28th.
As you can see, for someone with a regular, average cycle, in just eight months, they've got a pretty big date span with their periods that jumps around a bit.
Now, it may be that you're basing your dates on only paying attention just recently to when your period comes, or it may be that your cycles are NOT regular, and just happen to keep falling on those dates. But if you want to have an accurate idea of when to expect your period, you need to chart your cycles by a number of days, not by dates, so that you know to expect a period every 28 (or 26, or 30, whatever it is for you) days, rather than on X date.
That given, you may not be late for your period at all right now.
If you have had a real pregnancy risk -- if you know you had intercourse without using a method of birth control, or know or suspect your method failed -- then it's sound to consider pregnancy a possibility. If your last risk was less than 10-14 days ago, it may be too soon to take a home pregnancy test and get an accurate result. If that's the case, you'll need to wait until it's been around two weeks since the risk and then retake that test.
But if you took your test when it had been that long since your risk, or didn't have a viable risk at all, then it's likely you have no cause for concern here.
Just in case, here is a piece to fill you in on other common causes for late cycles, if you are in fact late: M.I.A or, Dude, Where's My Period?.
(And obviously, if you are sexually active and engaging in sex with risks of pregnancy, and do not wish to become pregnant, then it's very important you only do so using a reliable method -- or combined methods -- of birth control, such as condoms and/or the birth control pill.)