All it is is called spotting. And its for the most part when your on oral birth control pills this happens when you forget to take your pills on time.
Or maybe it could be the first sign of your period because you haven't been taking your pills as your doctor told you to take them. I would suggest that if you continue on missing your oral birth control pills and you keep forgetting to take them at the proper time you go to your doctors office and talk to your doctor about getting on a different type of birth control. This may help you out a hole lot because there are other birth controls you can take that you don't need to take every single day.
I am on the orth evera once a week patch, this is a patch you put on your body once a week. And it stays on your body for that one week and you change them. You have 3 weeks worth of patches and on the 5th week you take your patch off and go for a patches day week where you will get your period. I usually only get my period 2 days max. And then you put your patch back on the next week on the day you and your doctor have decided on.
For more information on this go to:
http://www.orthoevra.com
There are other birth controls to that you don't have to take everyday such as
-Nuva Ring http://www.nuvaring.com (you put this in for the hole month and don't change it)
And there are also injections you can take for birth control too.
Talk it out with your doctor. And if you want to stay on Oral Contraceptive pills then take them everyday at the time your supposed.
But for your question i would say its just spotting. If your not comfortable with it and your scared i would say go see a doctor
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http://chair-a-tee.myminicity.com/ind go to that link