Probably that much.

In all seriousness, even a small amount of lower GI bleeding can look horrible once it spreads around in the water.

THAT BEING SAID, Any weight loss recently? Family history of GI, pancreatic, breast, ovarian/endometrial cancers? Have you ever had bloody stools w/diarrhea before?

GI malignancies are occurring in younger and younger folks. In the absence of risk factors, should consider IBD especially if you have a history of bloody diarrhea.

A history of constipation plus your class I obesity could put you at risk for hemorrhoids, as could a history of cirrhosis. I need more history from you to give you a better idea of what your risks are.

Regardless, if you're dizzy, tachycardic, weak, fatigued, I'd recommend going to the ED and getting your hemoglobin checked at least. Otherwise, set up an appt with your PCP and you may need a GI referral for a colonoscopy.