How To Get Rid Of Pain In Penis?

Male 45 yrs married. After intercourse, if I do not wash and clean my penis. It seems that I get infection after a feel days. I get this burning pain in the evening. Pain get worse on the 3rd to 4th days and goes away after about a week. Funny thing is that, when busy at work, I don't feel anything. The pain come in the evening when I get off work till I goes to bed and goes off after a lot of discomfort. Sometime I feel like chopping it off. Had this problem for about 10 yrs. local doctors can't seem to figure out what's wrong. When I don't drink enough water, my bobby overheat and I get the pain too.