What are the chances?

If you are inconsistent at taking your birth control, i do not know how you would be able to determine when you should have your period, as this messes up your cycle. I can tell you i was very up in down with taking mine, meaning i would skip a month here and there, and then pop a bunch after unprotected with my BF, and i am now 6 months pregnant as a result. BUT if you take your birth control frequently (even if not every day and at the same time ) and you have been taking it longer then six months, i truly doubt you have anything to worry about, its really difficult to conceive when you consistently take those chemicals in the pill, alot of the time even after you stop taking the pill you have to wait for your system to go back to normal, and you are not nearly as fertile. You mentioned a discharge, and i have never read you form the mucus plug that early on in pregnancy, i have read that discharge sometimes takes place a week prior or so to starting your period. So from your post i would say you are not prego, but sometimes random pregnancy's do happen, (very unlikely if you take birth control on a frequent basis). If you were pregnant and last months period was "implant bleeding" (it would have been spotting, not a heavy flow at all) the pregnancy test would be able to detect that you were pregnant by now (its two weeks tops) anyways, wait two more weeks and if you still have not gotten your period, take another test, but most likely you system has been funky from your birth control use, and because you are ually active.