It's time to ramp up your pull-up. Pauses will help you gain strength in parts of the pull where you're weak instead of relying on momentum. Also, it'll stop you from swinging during the movement, forcing you to stay super strict.

Just pause each rep in the middle on the way up, at the top, and in the middle on the negative.

To make the exercise more challenging, try adding weight with a weight vest or by holding a dumbbell between your feet. And if you need some assistance, you can do banded pull-ups until you build enough strength to do them with bodyweight.