"Should I mentally be preparing myself for a positive result? "
You are WAY overblowing this. First, there's no indication that he is HIV+, and most people aren't, so that alone is statistically unlikely. Second, HIV is not that easy to transmit, and even in risky situations, the odds aren't even as high as 1%
Fortunately, you didn't have a risk as oral sex doesn't pose a risk (giving or receiving), even when blood is present. If there were a sufficient amount of blood to transmit HIV, it would not be possible for him to be giving you oral. In any case, HIV hasn't been transmitted this way in the over 40-year history of HIV, and you won't be the first.
Put these events behind you and move on. No testing is needed, but if you decide to do so, you'll get a negative since you were never at risk for HIV.