If a had oral sex with girl friend to whom i know ...

If you've had unprotected sex your chances of getting STD increase. If as you say your partner has never had sexual relationships of any kind, including oral or other forms of sex, you're probably safe on most counts, though it is still advisable not to have unprotected sex.

you could still get something from her, you dont have to have sex to get stds. for example, you could get it from using dirty needles [drug use, dr offices, tattoos, piercings etc] she could also have oral herpes or some other std that can be on or around the mouth. sometimes std infected people show no symptoms ever. and most of the time people do not show symptoms till many months later. really all you can do is take the chance. or have her tested to be safe.