Period or pregnancy?

So I started taking a progesterone only bc pill 2 weeks ago... After the first week(i started taking it the sunday after my period) hubby and I had unprotected sex bc pharmacist said after 7 days you are protected. Two days after having unprotected sex i was spotting for a few hours nothing serious... The past couple of days my breast have been sooo tender. Im so concerned this could be pregnancy however it is also a side effect of the progesterone only pill. Has anybody else taken the progesterone only pill and had this side effect? I take it at the SAME exact time EVERY day!