Iron injections

Hey , i'm 14 and i suffer from really bad anemia , i've been on 660 mg of iron a day for a year now , and my iron level is still only 6 , i have been under numerous consultants and dr's and none of them have seemed to do anything but leave me , i was going to be referred to hematology but they seem to think it will now not benefit me ( they were going to take regular blood tests hourly to see whether my body was ingesting the iron supplement). I saw my GP today and he has suggested iron injections in my arm , i have recently lost alot of weight and am fragile as i am also vitamin D deficient and hyper-mobile unfortuantly some of the side effects of hyper mobility is bruising easily . My hemoglobin is 11 and i suffer from a low blood count , and according to the peadeatrician iron injections were stopped due to the pain ,as i have now found out they are still available , can anyone tell me if they actually work and how painful they really are ? I would really appreciate it , Thank'you.