Welcome to the STD forum.
In general, oral sex is safe sex. Not totally free of STD risk, but much lower risk than vaginal or anal sex. You could get oral gonorrhea, herpes, or syphilis -- that's pretty much it. His belief he has no STDs lowers the already low risk still further, but there is no way to know for certain unless he gets retested. HIV is a theoretical risk, but average chance is in the range of 1 in 10,000 if your partner has HIV -- which probably he does not. Penis-to-penis contact is not likely to transmit anything, although I cannot say it is totally risk free.
All things considered, the STD/HIV risk is sufficiently low that you really don't need testing in the absence of symptoms. However, that's the only way to know for certain. You could visit your local health department STD clinic, or your personal health care provider, to be examined and tested. If you do it, you can expect negative results.
Best wishes-- HHH, MD
Sorry, one more thing: I haven't seen any symptoms or anything out of the ordinary at this point. This is more of a preemptive question.