Do I have a yeast infection or something worse?

Patient: I am a 19, almost 20 year old female and this is my first issue with my vagina. I think I might have a yeast infection. However, I am not sure… my vagina has been discharging an odorless curdy like substance. But, the substance is not white but like a light red brown colored substance. The outside of my vagina has been REALLY itchy, but Advil seems to calm the itchiness. Today I bought Monistat3… Should I use it, are there any side effects if I use it without truly know if I do have a yeast infection. Also, many websites have told me to go see an ob/gyn because this is my first infection of my private parts. Should I consult with a womans doctor? What should I do?