Hi, I'm suffering from the same strange embarassing problem. Been more than 15 years now. Just keep trying, you're not alone. We'll all get through it and have a good life again.
As to the exercising of the sphincter muscle try this link.
I found it while researching this issue. I can't say for certain this will stop it. But sometimes I DO feel that it has helped me some. At least in my mind.
I've slacked a little in the last 3 weeks doing this but, I think it has helped. Also if the muscles are stronger less gas or whatever may seep out.
Also, you might watch your fluid intake, except for water of course. I've wondered since I down Coke like its a vice that it goes through and causes the issues.