Can a woman still get pregnant if she is...?

Breastfeeding, on the birth control pill, and has used a condom every time? I haven't had a period since my daughter was 4 weeks old and she is now almost 9 months old. She is breast fed so I think that's probably why. I wouldn't think anything of it if I hadn't had heart burn and indigestion for the past 5 days, which is weird for me. I was eating a peanut butter and strawberry jam sandwich, which I usually LOVE and halfway through I had a sudden rush of nausea. I just don't know... I have been taking every precaution to not get pregnant. And I have NO idea when to test... Not that it would be a bad thing if I was pregnant. I want another baby, just timing isn't right. So, what do you think? Is it maybe just a freak thing? I might buy a test tomorrow...