No Gains

Hello. My English is not perfect but I can ask some advanced users who have many years experience. I do PE 10 years. First months and maybe 2 years I gain from 16.8 cm to 19.8 cm. Next 2 years I gain next 4 mm on 20.2 cm. But last 6 years I no gains. I don’t take longer rest days as 2 or 3 days . I do everyday jelq or advanced PE manual exercises. For example 2 years ago I use phalosan forte for 5months avarage 12hours dayly. I start with lengh 20.2 cm. Afrer 5 months of using I achieve 20.8 cm but immediately when I take break my lenght decrease in 2 days on 19.8 cm. So - 4 mm compare with origin. 4mm decrease ! During last 6 years I try water pump , air pump , extenders and manual excercises . I do it dayly no brake. Maybe 1 day rest in 2 week is awarage. Can some one with similar problems help how I can grows again ? Thanks for help.