Anemic and ulcerative colitis

Hey guys so back in July I had to get 2 blood transfusions because my ulcerative colitis. (My hemoglobin was 5.2) and now I am anemic again but I’ve been taking iron so how is that possible? I haven’t had any bloody stool since November unless it’s micro bleeding. I’m not sure what to do at this point because I have wrestling and my anemia makes me really short of breath. I was just wondering is UC causes malabsorption of vitamins or what’s going on here.

Thank you!