7 weeks post, pregnant?

I'm seven weeks post-partum, and as soon as I got the green light we had sex. I'm exclusively breastfeeding my little one. I've been taking the mini pill, which I've been warned isn't completely effective. It took me 6 years to get pregnant with my daughter...I've had some spotting, or it may be the start of a period. Could my period be this early? Or am I pregnant again? When should I test, since I'm not sure about when my period returns...so I don't know if I'm late.