I'm not sure what the odds are, but I know that my sister was on birth control for years and then in october she got pregnant. she's now eight months and due on july 19th. the doctor said the baby is progressing fine and healthy. everyone asks her if they we're trying and when she says no they ask if she was on the pill. she gets quite a few surpised reactions when she tells them yes!
I know they try to tell you the pill is 99% to work however it varies from person to person as I have discovered I am 18w6d and was on the pill. Have you recently taken any prescrition drugs as that will increase the risk of pregnancy.
I got pregnant on the pill too with my first baby, didn't miss any, took them at the same time, not on antibiotics (like mentioned above, they can decrease the effectiveness of the pill), still happened. Same thing with my mom, she got pregnant with my little brother on the pill. Nothing is 100%, and my Dr. warned me since it wasn't as effective for my mom it may not be as effective for me either. Of course my son was a wonderful surprise nad I'm so thankful for him, but definitely not a planned baby, my last pregnancy was not planned either...take a test if you are unsure they are pretty accurate.
I know pill and nursing hormones are different, but here is my story, maybe it will help you. My dd was 12 weeks old, and I got a light period. Lasted for about 4 days, mainly spotting. I did not think I could be pg since i ws nursing full time. About a week later I started to "suspect" and took a test - negative. I wainted another several weeks, and started giving some bottles, and got a positive. Moral of the story - it is definately possible to get light spotting with a viable pg, especially if other hormones are involved. I would hpt. Good luck.
I was on BC for 3 years and never skipped one. I got pregnant with my 1st daughter. 6 weeks after she was born, I started BC again. 4 years years later out popped my youngest daughter!
i took the pill religiously and got pregnant twice! .. both misscarridges tho