I've been cheating for almost 20 years
Are you serious? What was it that made you want to start to cheat in the first place 20 years ago?
I thought it would be fun.
Fun is where you find it and you found it in cheating. Cheating is sinful in some countries to the max. Go to a church and confess your sins for if you don't then God will take a wrath upon you in his own way which won't be pleasant.
Go on.
The guilt of this cheating will eventually wear on you so you should address the issue as soon as possible.