Considering scientific research into the risks of hiv, your risk is non-existent. Saliva does not contain sufficient quantitities of the virus to transmit, as has been proven. Saliva is also an effective barrier against hiv in the first place.

No one has been documented to have become infected with hiv from recieving oral sex in the 25 years of intensive research. No worries here.
If you wish to consult further expertise, I suggest you visit aidsmeds.Com, and post in the fears forum. A number of experts will be available to answer your question. They will tell you the same as I have.