Blood & Mucus in Stool. I be worried?

My stool has been soft for some time now (almost a month, or may be more). But there hasn't been any pain ever. I didn't take it seriously until on the 11th of this month I noticed fresh blood on the tissue paper. I was alarmed but it seemed like one of those isolated incidents as the blood disappeared the next day. However, on the 24th I again noticed blood after bowel movement. The tissue paper was stained red once again. From the next day the blood has disappeared again. the texture of the stool hasn't been consistent. However, most of the time it's soft, and often appears disintegrated. The colour too varies, from the usual yellow to blackish. When there's blood, I do not think that it is mixed with the stool. In all the cases, I ended up noticing the blood because it stained the tissue paper. While cleaning myself I almost always notice a mucus like substance on the tissue paper. Even if there is blood. My mother & paternal grandmother had Brest cancer. Should I be worried?