My 6 year old daughter had a few months of B.O. as well.  This prompted us to have her tested for late onset CAH.  The tests were negative (my son has CAH).  The endo. said some kids just have B.O. earlier than others and that it can come and go.  We haven’t noticed it in a couple of months now.  When she was having it though it was really bad - other kids on her basketball team even told her "you stink".  My daughter has not had any others signs of early puberty.  We had her start using deodarant (the kind for teenage girls) every day after her shower.  She has not needed to use it in a while. 

Have you had lab’s run recently?  If not I would definitely think it is time to have them checked. If the lab’s are ok then maybe se if it improves in a couple of months.

Lisa