It is important to take your birth control pills properly. If you just started them and forgot to take a pill, that can definitely elicit you to start bleeding. Make sure you read your birth control pill instructions... it'll tell you the protocol for missing pills and such. If your discharge went back to normal, then it's probably because you took the pill you missed, thereby telling your body not to slough. Make sure you do not engage in unprotected sex if you've missed pills (they say a woman can still get pregnant on the pill after the first week---when they are supposed to be infertile---because of imperfect use of the pill) and furthermore, protected sex is a good idea on the brunt of it.
i would call the dr. office and see what they would like you to do with you not taken the pill the way you should and if you are sex active you could be expecting or not but call the dr. they will tell you what he things it is