What Are My Girlfriends Chances Of Pregnancy? She Hasn't Had

What are my girlfriends chances of pregnancy? She hasn't had a period and has been having brown discharge for about 3 MONTHS now. We're getting worried and can't go get a test. We've had sex with a condom and birth control - LoLoEstrin Fe. BUT she's forgot a few times and took it a day later. What is going on here? Please help answer this with a lot of detail. :(