SallyQ

I'm not quite sure what you're asking, but let me take a go at it.
1. If neither of you has an STD, then neither of you can get an STD through regular sex with each other. However, if one of you gets cold sores on your mouth, this is a form of herpes. It can be passed from one partner's mouth (the one with the cold sores) to the other person's genitals during oral sex.
2. Ejaculate has little to do with the transmission of many STDs. For example, both herpes and genital warts are passed by skin-to-skin contact. Thus, it doesn't matter if he ejaculated. In fact, it can be passed just by two people being naked together without sex ever taking place.
3. If he has genital herpes and you give him oral sex, you may get it on your mouth. You don't need to have a cut on your mouth.
Lastly, (and this might as well become my regular speech) ANYONE who has sex can get an STD. Most people will get one during their sexual lives. Please don't be so naive as to think it's only strippers and "dirty" people who get them. Education about STDs is what's really needed to get rid of this silly stigma. If you're worried that you may have been exposed to an STD, please see your doctor. He/she is the only one who can accurately diagnose you. Good luck.