Skin will need to be stretched before there’s room for size increase. Your goal is to hit the ligaments and you will get feedback on this by how you feel after your training. Are you getting any kind of soreness at the base of your penis? I’m asking because this may be a case of needing a better grip. In that case I recommend the
Lengthmaster. But at the very minimum use baby powder or rubber gloves to get a good grip.
What are you doing for a workout? Meaning what exercises specifically how much time how many reps, etc.?