I'm catholic. If you are trying to be all religous and stuff than no that would not be acceptable as it is considered adultery--which includes basically any stimulation of the genitalia outside of marriage. Even masturbation. Personally im not very religous and really dont give a damn what the church has to say about my life. But if you are trying to be a good catholic boy than no oral sex would not be permissable. Neither would jacking off or even touching her boob.