Can I catch HIV if I use a condom and she is on acyclovir?

Acyclovir reduces the chance of getting genital herpes outbreaks. HIV is spread through semen, vaginal blood and if her blood enters your body. If you use a condom the chance of catching HIV greatly reduces. If she performs oral sex on you HIV won't spread. HIV isn't spread from saliva. If you perform oral sex on her HIV could spread if she carries the virus (seem HIV is found in vaginal fluid).

How big of a risk for getting oral sex from HIV positive person?

HIV is typically spread by exchanged semen, vaginal fluids and blood. If a partner with HIV performs oral sex on you the chance of catching the virus is very low. If a partner with HIV performs oral sex on you that person's semen, vaginal fluid or blood wouldn't enter your body. The chance of catching HIV in that situation is almost non existent. If a partner has any open cuts in his or her mouth I wouldn't suggest having oral sex. Having safe oral sex always reduces the chance of passing or catching an STD. If you want to read more about HIV go to the following website.