Long Menstrual Cycles and Anemia

Back in 2018, I had a cycle that lasted over 2 months. Heavy flow the entire time. It went off and then came back on a month later and stayed on for nearly two months straight. I became severely anemic. I had to get a blood transfusion. It helped, but as long as I had the long periods, it wasn't any use. They prescribed me iron pills and birth control. The iron pills did not help much. They just made me constipated. and the birth control pills gave me depression and I had a lot of crying spells(I already had anxiety due to lack of oxygen in the few red blood cells that I have) The birth control pills regulated my cycle for a while, but after a while, I just stopped having menstrual cycles. I often forget to take my bc pills. When I don't take them for a while, my period starts out of nowhere. once I had two menstrual cycles in the same month. but when I took them again, my cycles stopped almost immediately. Can someone tell me what this is or what I should do?