A method you might not have tried to gain some muscle on your chest is this type of combo lift.You are going to be basically taking two exercises and performing them back to back. First set up a incline bench and grab some dumbbells. Now perform incline chest presses until you have about 2 reps left in the tank and then bring the weights down to rest on your thighs. If you are able to do more than 10-12 reps than you should increase the weight. After you rest the weights, have someone drop the bench so it is flat and then perform chest presses until failure. use the same weight on both the incline and flat press. There is no rest between the exercises other than to change the bench. This routine is really tough and flat out sucks. I would recommend doing 3-4 sets of it. Remember that the flat bench part of the combo will be the toughest since your chest will be pre-fatigued.