Sounds like you have a yeast infection, or a bacterial infection. There is a test you can by that will tell you, but if it is a bacterial infection you will need to see a doctor. If it is a yeast infection, you can try monostat or one of the other yeast infection medication that you do not need a perscription for.
You'll need to see a doctor to get prescribed the medication for this infection. It sounds to me like you have a bacterial infection of some sort, and since there isn't any one cause for them, you'll need to go over your recent sexual health history with a doctor to find out. Good luck!