What Causes Rashes On Foreskin?

hi, im 30yrs old male, i find clusters of skin coloured rashes on my penis foreskin, it appears when retracted back. when my penis is erect can see some red rashes on head of penis , i had unprotected oral sex when i was in first yr of my college. not had sexual intercourse yet. Im not sure about what infection im having. It is not creating any problem in mastrubating , if i marry , i feel im at risk of spreading this to my partner, pls help ..