when should i be concerned of pregnancy with irregular periods and birth control

[leigh1425]

before birth control it was never spot on every month, but once i started to take it, of course that changed. i had it weeks later in the month towards the end rather than before, when i had it pretty much at the beginning. that's not a shock with birth control, though. i've missed my period the month before last month, had it the following month, but missed it last month. now, it tended to come around the end of the month again. i went to my gynecologist because it was my first time taking birth control, and of course, i was worried about pregnancy since i missed it. but she told me i wasn't pregnant, took the test and the whatnot. i didn't feel like i was, but i asked anyway why i might not have bled. i got all the pains, and i told her that. at one point the pains were near unbearable, but i just got over it, granted i told her about that, too. she told me my body was trying to have my period, and that's why i had the cramps- but no blood. really, i didn't get an answer but i got the idea overall. so, i'm having the pains again, and as i mentioned no period last month- granted i had the pains then, too. i usually get the pains or sore breasts two weeks in advance at the most. and that's about the time. i think i was told by her that if i miss it twice a month to come back, because there might be something else. my main question is if i should be concerned about my health and pregnancy. it looks like yesterday or the day before i accidentally took two birth control pills. so i just took one of those extras in the back today, to keep my body used to it still. tomorrow is my last day, then i wait a week, and start up on it again the following sunday. i don't feel pregnant in the slightest, but even knowing i have an irregular period, i can't help but worry still about it. there are no signs, though i have the slightly sore breasts, though that's fading now, and the usual pains from cramps. if it doesn't come this month, would could it mean? aside from pregnancy, i've already checked that.