Provera question!

I've taken provera many times to regulate my cycles, and have never had any problems starting my period. Typically I would start 4 to 5 days after taking the 10th provera pill, but this time, all I'm having is red/pink spotting. Took a couple pregnancy tests before I started taking provera and they were negative. Is it possible to get pregnant while taking provera and is it possible that I am?