First of all everything has been "brought up before" so don't worry about it. It's actually a very good question.
Everyone's system is different. You'll have to experiement in order to find what works for you. It could be that you are feeling overtrained, not because of the actual workouts but because you have other stress in your life, not sleeping properly, not eating properly, (protein consumption is down), etc. Any of that sound familiar?
As far as routines, one of the best that I have ever seen was created by the late Bob Hoffman, founder of York Barbell and Olympic team weight lifting coach when the USA actually used to win Gold medals!
It's called "Heavy, medium, light. And as you might have guessed already you train three days per week-full body! One day is heavy, one medium one light.
Plenty of guys added plenty of muscle on this system and they did it without using drugs!
If you give it a try let me know how it works for you after 6 to 8 weeks.