I mean you won’t know your penis well enough to understand why you might not be gaining. Understanding the basic anatomy of the penis is a good first step.
Jelqing is very different from stretching. You’d have to get good at it to really appreciate it, there’s quite a learning curve.
Stretching you can think of as applying a force to the tissue in a single direction. The majority of stretching is done fairly statically. There’s the JAI stretch which works dynamically but still the force of a stretch is applied generally between the base of the penis just behind the glans. This is great, there’s lots of stuff that will be affected by that but tissue adapts to stress.
Jelqing is different. It’s a dynamic exercise that stresses above the point of the grip with internal pressure against the walls of the CCs and passes a wave of different forces up the shaft at the point of the grip with each stroke. You can think of it as a combination tenderising and internal pressure exercise.
Part of the problem with penis enlargement is gauging the right amount of stress to apply in the right manner at the right time to grow. For some reason and I wouldn’t say it’s obvious to me why this is the case, too much stress appears to be as bad as too little.