Suggest Remedy For Penis Problem

I am 24 years old, 5 ft 8". and have a normal physique. My penis is 5".. I have seen that the foreskin normally slides back, however mine doesn't. I can masterbrate normally and everything else is normal. But I wonder if whenever i have sex, and if its a tight vagina, it might be painful for me as the foreskin doesn't slide back. What do i do about it? Secondly, from past 3-4 weeks i have this rash next to my pubic area, and it itches a lot.. I used to apply sulphur (homeopathic) and it used to ease for a while but again used to come back. I am very hygienic and wonder what this can be.