What kind of fungal infection or std cause internal pain in the anus penis and scrotum. i also have a rash in and around anus.?

Hmmm: If you have chlamydia or gonorrhea it's possible. You would have likely had anal sex as well to get anal involvement. A rash could be due to another infection.

Fungal infection?: What makes you think that it's a fungal infection and not std? You need to see a md to run proper tests on you to make right diagnosis and then give you right treatment.