Firstly I think you need to see your dentist to diagnosis the possibility of periodontal disease.As I have stated it is a disease process and although you might be meticulous in your oral hygiene that does not always prevent this disease. It certainly is important to floss and brush, the normal bacteria in your mouth can be causing this disease no matter what you do. It is an autoimmune disease.See your dentist asap.
the usual reason for bleeding gums is gingivitis or periodontitis. a visit to the dentist is in order so that the problem cn be evaluated and treated. there is nothing you can buy to put on your gums to fix this problem. It needs to be handled professionally, and then you need to be taught proper homecare.