Thanks for your query.
As you provided the detail,it seems that you have gum disease
,as you said that this recession is very rapid since last six months,it is not a good sign.
The details provided by you are not sufficient you did not provide few details like-
There are few follo0wing possibilities-
2.poor oral hygiene
5.oral habits like,grinding/clenching teeth.etc........
So i will suggest you please visit your dentist
as soon as possible to rule out the diagnosis and take a proper treatment.
Nothing to get worried.