Shiny Irritant skin on base of penis shaft! HELP!

i am 25 yrs old & for the last 6 months or so i have been having extreme discomfort with a skin problem at the base of the underside of my penis shaft. At times the patch of skin it has affected seems thin & shiny, and is very red and extemely irritant. masturbating & intercourse makes it worse. when left to try and heal it will start to heal and get quite flaky skin over it, but always eventually just goes back to being raw and irritant. Its at a point where its driving me crazy in public. i also feel at times i have to refrain from having intercourse with my partner.  

also i have a small patch on my scrotum for the last 6-10months where it seems quite similar. very itchy & irritant but not as painful as the skin on my penis. i did try using some steroid cream on these areas but did not seem to work well keeping it away. although did help solve the problem some at the start. Also the skin around my anus and between anus & scrotum can be quite irritant at times.

i am quite sure i dont have an STD, as i have been with the same partner for the last 7 years & have not had sex with anyone else since then. i suspected herpes at the start but have seen images of herpes and quite convinced it is not.

Can anyone please help with what this could be?? or any treatment or advise i could use to clear this?? I want nothing more to get rid of this rash/ skin problem on my penis! i can add a photo if needed!  Thankyou!