Manal, thanks for further explanation, very clear to me now.  
Andy, I dont really remember about my Hb level before pregnancy, while doc found my Hb was 7 on pregnancy, he gave iron supplement without checking first why my Hb was 7, then checked again a month after, it was still 7, then he sent me to lab to check the blood further.  Result found that red blood cells were microcytic, anisocytosis, poikilocytosis, polikromasia (+), target cells (+).
But i do remember i easily got tired since i was teenager, sometimes my breath were short, and when got too tired or sleepless then i felt palpitation.  Heart beating so hard, and head aching severely. 
I am going to Singapore this end of month, to have complete medical check up.  Will come back to you guys, to let you know the resut.
Thanks so much, now i know what i should discuss with doctors.  You all have been very helpful. Thank you.