Hi there ~
I understand your concern. It is unusual to have painful brown pathes on penis and the fact that it is spreading is even more concerning and sounds like herpes
. You need to see a dermatologist
immediately. It may also be that your penis hurting while urinating may be due to a urinary tract infection
(UTI) or due to a sexually transmitted disease
(STD). In either case you would have to visit a doctor. If testing i.e. screening for STDs are normal and you do not have a UTI either you might have a benign or a malignant urological condition for which you need to visit with a urologist
. I hope this helps. Take care and have a lovely day!