A lot of blood during bowel movement. what can i do to stop this?

It depends : If blood in the stoll is red, it may be from a hemorrhoid. This needs to be evaluated and treated, but is fairly common. If the blood or stool is darker (black) and has a 'tar-like' appearance, it is more indicative of a bleed in the upper areas of the GI tract. This is more significant and needs more prompt evaluation and treatment. The larger volume of blood dictates treatment asap.