Concern and curious!

Ok....can someone tell me, before you actually know that you are pregnant, what does your bowel look like because I feel pressure like I have to take a bm but nothing come, however when I do go my bm is like breaking into pieces. Is that normal you think? My period suppose to come on this Sunday but I will see what happens because I am getting symptoms like crazy but it maybe associated with my pms. Tell your thoughts please! Also could that be a sign of pregnancy?