What Causes Red Rash On Penis Head?

I am 20 years old and only been with 3 partners and about 8 months ago I noticed I have a mild red rash that's almost wrinkly on head of my penis I'm circumsized and have yet to see a doctor .. I read some forums and I don't think it is anything to worry about but still little worried .. and also if I stretch the skin non erect the wrinkles appear more red then get lighter but have never gone away... any ideas?