sometimes you can have an increase in discharge just because you had sex. i know that it sounds strange but its happened ever since the first time (I was also 16). im 20 now. I dont think that you have anything serious to worry about. :)
having protected sex will help with that also. even if he does pull out, the secretions from men can throw off the pH levels inside of you which can cause discomfort. < just a little tip!