Hi reemhanna,
Welcome on the forum,you are right about iron intake,thal minors should not take iron in supplement form unless its proved that they are iron deficient,you can ask you doctor to do iron studies for you so that it can be determined whether you have iron deficiency anemia,which can co exist with Thal minor.
Your hb is a bit low,but most of thal minors do have to live with that hb,i am a thal minor and my hb always hovers around 10,what you can do to improve it with out taking iron is taking folic acid daily.For fatigue,try a good Vitamin B complex,it helped me A LOT.And wheat grass is another alternative if you wanna try it,it will definitely give a boost to your energy levels.
About your thyroid problem,i am sorry i don't know much,but this sudden weight gain does seem like thyroid problem,wait for our administrator Andy's advice on that.
Hope this helps.
Zaini.