Chances of getting pregnant when tubes are ligated are poor because it is one of the most successful method of contraception. Breast tenderness can be one of signs of premenstrual syndrome which is common and majority of ladies. Blood clots develop due to inhibitory factors produced by our body in order to reduce blood loss. As during periods, blood is lost and our body respond according by producing clotting factors but this bleeding is also normal and needed, so, our body also produces some factors that cause thinning of blood. When clotting factors are in higher number than factors that cause thinning of blood then clots are produced. In my opinion, you are not pregnant but satisfy yourself by taking pregnancy test.
Heavy blood clots could mean your not drinking enough water before your period,,the blood is thick on the walls of you uterus and the water helps it thin out to pass..