My partner is positive and I am negative. When we practice anal sex, we use condoms. When I am giving him oral sex, I like him to ejaculate in my mouth. I know that this is riskier than if he didn't, but doesn't saliva and stomach acids kill the virus? I check my mouth and gums before and they aren't bleeding. He gets really upset when I swallow. I was told by a clinic that although this practice has risks, it isn't that high...

It is true that unprotected oral sex, even with ejaculation, is not as high as unprotected anal sex. However, there is risk. You've been lucky thus far, however, it is possible that you could become infected with this behavior. I'm concerned about the fact that your partner gets really upset about this. This cannot be pleasant for him. Most HIV+ people in mixed status relationships have a lot of anxiety about their partner becoming infected. I think you should take his concerns seriously and try and understand how he feels. Perhaps both of you can talk together with a counselor about this so that you come to a mutually agreed upon understanding of behaviors you can both be comfortable with, and that you can both also be sexually satisfied.