What Causes Burning In Tip Of Penis?

Alright, i recently turned 16. 4 days ago, my Tip of the penis head the skin.. started burning when I touched it or it rubbed agianst my Underwear, its not that bad anymore, i can hardly sence it. but this white substance is comming out from my penis skin. not out through it, but like an ejaculation, (Havent had sex yet)