I'm a hypochondriac and i've convinced myself i have hiv from mutual masturbation. is this possible? hiv risk from semen getting into hang nails?

Improbable: If you have open wounds/sores and or your partner had the same, you could pass something like HIV between you. However, this germ is sensitive to rapid inactivation if it is outside the body, and semen is not the primary carrier. It is the abrasive mechanics of sex that brings skin surfaces with serum or blood that would pass the germ.Using tainted toys could also pass germs.

Seek HIV counseling: Read online or seek live counseling and even a test to calm yourself. You don't say if your "sex-buddy" is HIV positive. If not, there's no risk for sure. If unknown, they might test too. If positive and your hang nails aare openly bleeding there's a small risk - very small. Consider CBT therapy to help w/ hypochondria. Best!

Glad u have insight: If a hangnail is not actively bleeding, it's protected by a layer of fibrin from infection. You're not going to get HIV that way. Remember that the large majority of wives of HIV-positive husbands, before there was treatment, having unprotected sex did not convert. Cognitive-behavioral or other therapy for your hypochondriasis would be a wonderful gift for yourself. Be brave & go for it. Cheers.