You should see a doc. If you have a yeast infection you can treat it with otc medication. But if you're not sure what it is you should see your doc because if you treat a bacterial infection with yeast infection medicine, you'll make it worse.
Also, untreated bacterial infections can lead to pid, which is serious.
And some std's can be dormant for a while.
If you're ever not sure what you have, you should go in.