Have you been to your dentist for this? What they usually do is deep cleaning under the gumline first (sounds painful but they numb you, you don't feel a thing....really) and afterwards more frequent cleanings, possibly every 4 months instead of 6. You really don't want to let this go as not only could an advanced case possibly lead to oral cancer later on, you will probably eventually lose your teeth. There's really nothing you can do yourself to get rid of it, but once you're on a schedule with your dentist, simple flossing and brushing will help along with your dental cleanings.