Please help.. it’s been going on for a while.

So my discharge is clear most of the time but sometimes it does get like really white and I feel like I might have a yeast infection. Sometimes it has streaks of yellow but I’m not really sure what’s going on down there. I’m starting to get really worried that I may have serious problems going on because my skin around my vaginal area and a little of my thighs are really dark too. I’m too skinny to have this because of thigh rubbing right? I am in track so I don’t know if that makes it worse when I sweat.. please help