Can u have a tear in rectum(not anus) from constipation+weak pelvic floor?no blood, muscles in low back tense from it.how to tell from serious piles?

Yes, but..: Hard stools is the most common cause of an anal fissure, a tear of the lining of the anal canal. It is usually very painful, especially with bowel movements. Might have a little bleeding but usually not much. Serious piles are typically only intermittently a problem. If tissue prolapses (comes out through the anus) or you have bleeding then they should be treated. Weak pelvic floor at 22?

Hard stool can tear: The anus is part of the rectum. It is the point where the skin joins the intestine. The lining of the intestine joins the skin and it can only stretch open a limited distance. If forced to open wider to pass a very hard stool, the lining/ skin will tear and cause a fissure. This is different than piles - which are hemorrhoidal veins that dilate (varicose veins).