Pooping big blood clots and feeling the toilet with blood what could be causing this?

Go to the doctor. You need to be evaluated for lower GI bleeding. It could be hemorrhoids, diverticulosis, colitis, inflammatory bowel disease, or cancer. Some of these can be very serious so you need to go to the doctor as soon as you can.
You have two issues. To e concerned about. First, you have to figure out the source of he bleeding. Second, you probably are anemic, maybe even severely. You should check in with your doctor right away or go to an er for evaluation.
Source? If vaginal see you gyn, if from the rectum see a gastroenterologist. Would be seen as soon as possible. If feeling poorly go to the er.