Do you want more muscle mass? You need to remember this important point when you are training: doing the exact same thing for a long time, lifting the same weight for the same number of repetitions, will not force the body to adapt in any way. After all, it has become pretty comfortable stuck in that groove.
You have to keep striving to add weight, you use, to keep the muscles under constant stimulation. The principle of progressive overload is universally accepted as the model that creates the greatest gains in strength.
The body will respond more when the weight is increased for the same exercise, versus switching up the exercises on a frequent basis but using the same relative amount of weight.
Progressive resistance, does not mean you add 10 pounds a week to your bench press. It may take a while to make strength increases, but just stick with this plan, even if it is only five pounds a month; at least you are heading in the right direction.