While having sex with a man he inserted his penis into my rectum. I realized that he did not have his condom on any longer. I immediately told him to stop and he did. He was only inside me for about 15 seconds. I know that HIV is an opportunistic infection and I was hoping that you could give me some perspective. I have been so scared that he could have been HIV positive. Even if he were what would be my risk of contracting HIV from that incident. I am a very scared woman. Please don't over look this question.

Let me start by perhaps clarifying your comment about HIV being an "opportunistic infection." In the context of HIV disease, an opportunistic infection usually refers to an illness that inflicts a person living with HIV, as a result of their immune system being suppressed. The opportunistic infection (such as pneumonia or toxoplasmosis) takes advantage (so to speak) of the weakened immune system, making the person sick -- therefore it is referred to as an "opportunistic" infection. But more importantly, to the point of your question -- HIV is a virus that can be transmitted when one is exposed to it via mucous membranes or direct blood contact. The incident you describe does carry some risk for the transmission of HIV, if that man was HIV+. The risk of transmission is lower when there is "limited" exposure. That means that reduced intensity and duration of contact is less likely to transmit HIV. Risk from pre-cum exists, but is not as high as when there is ejaculation. Nevertheless, the only way you will know if you have been infected is to be tested. If you have concerns you should speak with your physician and/or an HIV counselor and follow their recommendations.