Just noticed there is a rather large patch of brown-ish skin on my penis that i don't remember being there before. it looks very odd. i was alarmed but after researching, could this be ''penile melanosis'', a harmless skin pigment condition? am i ok?

You could watch and wait. If any nodules develop, and ulcer forms or bleeding occurs, see a doctor. It may just be extra pigmentation in the genial area that is normal. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV vaccine. Wish you good health!