I Have Frictional Burns On My Penis In 3 Places.

I have frictional burns on my penis in 3 places. I have been with my partner for over a year and a half and never had any problems and have remained faithful. My symptoms are now, a lump in the groin area, 3 burns (one on head and 2 on shaft) and a very painful time urinating. Nothing else seems out of line but it is making life more uncomfortable as well as affecting my relationship with my girlfriend due to our sex lives being affected. I believe that my partner has also remained completely faithful and couldn't even imagine a time where she could have been. Any help would be appreciated. Regards