3. YOU'VE GOT NO STRUCTURE
Remove the randomness from your workouts and stick to a plan. This is the best way to improve strength and increase muscle size. Random training might make you strong (for a beginner), but it's inferior to a planned periodized training program. A linear periodized plan can look like this: week 1: 3x12-15; week 2: 3x10-12; and week 3: 3x8-10. A non-periodized plan can look like this: weeks 1-3: 1st set 10-12 reps; 2nd set 6-8 reps, 3rd set 3-5 reps. Pick a plan and stick to it for maximum gains.