You have anemia
is 8.2 gm% in your case it is due to excessive blood loss during cyclical periods as you took iron injection.
You should be treated in two ways supplementation of iron orally if tolerated continuously at least for 6 months(100 mg elemental iron) if iron is not tolerated orally it may be given in injection form also.
Please also take care of your diet take lot of green vegetables,fruits,and nuts.
Other aspect of treatment would be to reduce blood loss hormone therapy
as advised by your Gynecologist,discuss with your doctor.
Any IUCD will not cause weight gain which is related to your diet and physical activity.