My hb has been 7 or 8g/l for the last 3 months or so. i have been experiencing a lot of breathlessness, palpitations and left side chest pain?

Anemia: You seem to have quite a profound anemia and may need to have a blood transfusion. Go to an er and get evaluated there. You are on iron so it seems that even with iron supplementation, you can't raise you hemoglobin. In the er , they can make sure you aren't losing blood either in your GI tract or your menses by excessive bleeding. Another cause could be that your bone marrow isn't making red cells.