when i lived in australia and worked in a job were you had a shower every day after work, [ i still shower everyday a good habbit try it /it wont kill you..] i was told by the cleaver aussies who could teach us brits a bit about hygene] don't wear under-wear or socks that have nylon in them as it will fire up your privates +feet.. don't let the hair under your arms grow long keep it very short or you will smell like a pig.. when drying off after a shower do the head-first then the body then the feet including between the toes , DON'T use the towel again ,if you have athletes-foot you will spread it to your privates etc.. don't share towels.. when showering ALWAYS finish off your shower in COOLER- water to close nerve-endings and stop-prically-heat [ RASH ] DON'T use talc at all , but get more air around the trouble areas...try to use mild-soap with no deoderant or colour in it..if you can swim in SALT water it's good for these problems..
My BF has had the same kind of problem. His doctor said to replace all underwear. Also wash down there with a mild soap after anything that makes you sweaty. The doctor also told him to wear loose cotton shorts to bed that breathe. My BF also sprays the inside of his boxers before he puts them on with a jock itch/athletes foot spray. It dries to a powder texture. He hasn't had it come back yet - it's been six months. Hopefully it's gone for good!