Pregnant?

I'm 15 and I've been on birth control for awhile now. I have frequent sex with my boyfriend of almost 3 years. We used to use condoms almost every time but lately have stopped. I always trust him to "pull-out" but sometimes I feel like he does it at the last second and some still gets inside of me. I'm currently on my blue pills (the period week) and I have a light flow and it's dark red. I don't really understand what this means. Am I pregnant or is this normal? I've also had tender breast for the first time in awhile. Thanks!