Welcome to thundersplace JonS. The correct way to measure your penis is “consistently.” Some guys with an excessive bend choose to use a flexible tape. The problem with a flexible tape is that as it reaches the end of the penis, it curves downward and measures slightly larger.
So, pick the way that works best for you. Make sure that measure a few times to make sure you are getting accurate/repeatable measurements. Then, just measure the same way to track your progress.
Good luck and good gains.
PE for length: so her heart stops when she sees it. PE for girth: to get her heart started again!
One need only leave the surface of the planet to realize we are all one people.