The risks and ONLY risks for contracting HIV are to have UNPROTECTED vaginal or anal sex (with penetration) or to share IV needles to inject drugs. Those are the only risks. Air and saliva both inactivate the virus. This is why no one in the history of HIV has gotten it from giving or receiving oral sex or kissing or touching.
With that said, if you are in a relationship with someone that is HIV positive, you need to get educated. If every time you are intimate with him, you freak out and wonder about hiv, this won't work. Unless you have unprotected anal sex with him, you aren't at risk. If you plan to have unprotected anal sex, Prep is something to talk to your doctor about. Glad to see you are discussing this.
But you can't get HIV from kissing, oral or anything else like that.