ok, i'm 15 never had period or anything and i'm just starting to get pubic hair. recently i've been getting discharge that's kinda gooey and it "stretches" - looks similar to what a slug leaves behind... any ide what this is?

P.S- i'm 90 pounds and 10% body fat (i'm tying to gain some weight)

i was told to gain 10-15 pounds and in 3 months i've gained 8 pounds:) so i'm trying!