Guy friend who is convinced he has H.I.V please help me.?

Hi so my guy friend has been driving me absolutely nuts lately with his hypocondriac related thoughts. Around april he had unprotected with a promiscuous girl and she happened to be menstruating to when they were doing it. ( they were drunk) Ever since hes been worried about h.i.v and how he might be infected. Soo after months of nagging him to get tested in july he got tested for H.I.V and thank god its negative. But he still isnt convinced! I mean i dont know what to do anymore obviously the girl did not have hiv since he came out negative right? Especially since there was blood and l fluid involved. I dont know what to do to help him. Please give me answers.