Hi Zaini,
We experienced something similar last year - this situation resolved quickly and was explained by activities that I overlooked.  Please see:
Thalassemia Patients and Friends / Discussion Forums / Thalassemia-related Issues / Bruising with Rituximab - please help
You can also see the blood tests that were suggested in that thread - by Andy and Sajid (sigh..).  
I hope that our princess heals very soon.  Andy suggested that I give lil A plenty of fruits and vegies and that did help.  
Best,
Sharmin