There is a finite number of exercises. The key is to change the order both of the exercises and the days in which you do the exercises. The more you mix and match, the better the overall results. Additionally, if you write down each workout and build a plan, it is more likely that you will stay more engaged mentally. You will be able to track your exercises, weight and see improvements.
For Example 4 Day workout 5 week block #1:
Day 1 - Chest Back Shoulders:
Flat Bench 5x10;
Incline 3x10
Lat Pull Downs 5x10;
Bent Over Rows 3x10
Military 3x10;
Standing Side Lat Raises 3x10
Day 2 -
Legs & Arms:
Squat 5x10; Stiff legged dead lifts 3x10
Standing Barbell 5x10; Preacher Dumbbell 3x10
Day 3 -
Chest Back Shoulders
Incline DB Press 5x10; Pec Deck 3x10
Pull-ups 5x10(to failure); Seated Rows 3x10
Seated Dumbbell Press 5x10; Shrugs 3x10
Day 4 - Legs & Arms:
Leg Press Sled 5x10; Hamstring Curl Machine 3x10
Seated Dumbbell Curl 5x10; Standing Cable Curls 3x10
Block #2
Day 1 - Back & Arms:
Dead lifts 5x10; Bent over barbell 2x10; Stiff-legged Dead Lift 2x10
Day 2 - Chest & Shoulders:
Decline Bench 5x10; Incline Dumbbell Press 3x10
Seated Military 4x10; Standing Front Lat Raises 3x10; Upright Rows 3x10
Day 3 - Legs & Arms:
Squat 5x10; Leg Ext 3x10; Hamstring Curl Machine 3x10
Standing Dumbbell Curls 5x10; Seated Curl Machine 3x10
Day 4 - Back, Chest & Shoulders:
Super-set - Pullups 5x10 (To Failure); Dips 5x10 (To Failure); Pushups 5x10 (To Failure); Shrugs 5x10(To Failure)