If you are a skinny guy and you want to build muscle, you know how difficult that can be for you. It is always a struggle to build muscle and gain weight. However, if you're not able to do so, that is because you're making some mistakes. These mistakes are stopping you from building the muscle you want.
Mistake 1: you not following the law of progressive overload
If you want to build muscle, you will need to know and understand the law of progressive overload. If you're using the same weights for the same number of reps, you'll not be able to build muscle because you are not forcing your body to adapt. You're simply wasting your time. People who build muscle are those guys gain the most strength. You need to be able to get consistent strength gains on a regular basis from the workout that you are following. If your workout doesn't focus on the law of progressive overload, you should immediately stop doing that and change it with something which will focus on progressive overload.
Reason 2: you are not using enough frequency
Even though your training, you are not training with enough frequency and that's why you not able to build more muscle. The more frequently you can train a muscle the faster you will grow. You will need to train a muscle while it is still recovering and getting stronger. It is generally seen that different bodybuilding programs have you train each muscle only once a week and that is not enough. If you are training each muscle group 2 times more than that, you can spare twice the results.
Reason 3: you are doing too many reps and sets
If you are performing too many sets and too many reps in each of them, you will not be able to grow more muscle. If you're trying to copy the workouts of pro bodybuilder, you need to understand that it is not possible to do so without using steroids. Such a workout can be too much for a skinny guy like you who wants to build muscle. There is absolutely no reason to do so many sets and reps for different body parts. To build muscle, your goal should be to get in, perform hard and do slightly more than you did last time so that you can stimulate the muscle growth process and get more muscles.
Reason 4: you never cycle your training
Even if you perform all the workouts with lots of intensity, it can be difficult for you to build muscle if you are a skinny guy. You do not need over training, injuries and burnouts. There is a limit to which your body can endure. To build muscle, you need to train hard but that should be done in a smart man. You will need to slowly increase the intensity and then give your body a break and then again push forward where you need to exceed your previous bests. It should work in a cycle and you need to understand when to do the different parts of the cycle.