Hi!
I am not sure why you are on blood thinners, but it appears that you are bleeding inside. This could be the cause you coughed up blood. You need to get your INR and prothrombin time done if you are on blood thinners and need to adjust the dose of blood thinner accordingly. Get a stool test for occult or hidden blood to confirm that you have gut bleeding. You could also bleed into the lungs. Hence please consult a doctor immediately and find out if you are bleeding inside, and to rule out other causes of anemia like vitamin B12 deficiency. Take care!