Iron Deficiency. Can treatment stop working? Can it be a sing of something searious?

[Urszula874]

Hi! I am twenty-one year old female. I have an iron deficiency anemia that has been ongoing and coming back every year for the last four years. Doctors haven't found a cause for it yet, but the investigations are ongoing. My gp already did some blood studies and discovered that by blood cells quite small, which if i am not wrong, means that the iron deficiency has been going on for quite a while and they also ruled out sickle cell disease . I am pretty sure that its not just the fault of my periods because first of all my periods never been that intense to cause such an ongoing problem that is getting worse second of all i starting developing other symptoms such as: unexplained weigh loss, changes in bowls habits. Anyway i was started on Ferrous Fumarate and it seemed to be going well. I regained my appetite and i had a bit more energy but for the last week the symptoms of the deficiency came back. I am feel really tired again to a point that every day in the afternoon i struggle not to fall asleep and also my appetite has got worse. Is it possible that the Ferrous Fumarte stopped working? Should go back to my gp or should i just wait and see if it just gets better on its own?
Oh also few days ago i had an attack of a sudden sever stomach pain in lower, i think, right abdomen. It was so intense that i couldn't move, stand straight or take a deep breath for an hour. I always had a sensitive stomach and i experienced a lot of different stomach pains in my life but it never ever was that intense and sudden and it also for sure felt different to others. It got better after about two hours but it still sometimes doesn't feel quite right but it got better so i never went to the doctors. I am not quite sure if it can be in anyway connected to the anemia or the weight loss? Can this anemia be a sing of something more searious thats getting worse and strating to cause abdominal symptoms?
I am just not quite sure what to do or what is actually happening.