What Causes Tender Breast And Bleeding After Pregnancy Test Shows Positive?

my breast have been tender for a month. Usually this happens about a week before my period starts. The 2nd or 3rd week my period started (or so i thought) but not heavy, but lightly. Now i have been doing this bleeding for 3 weeks. I have taken 3 pregnancy test in 3 days and they all show positive. please tell my what may be going on