Reduced erection size over the years is freaking me out. Does this return after recovery?

I notice that my erection size has been reduced by 1.5" inches to almost 2" inches in length compared to over the years when I was younger and not fapping. Does penis size shrink as we get older? (I'm 41.) Or is this in direct cause from my PIED? I feel like my penis isn't at full strength hardness and hasn't been for years. But then again, there are times where I've had a raging boner during masturbation, but then I feel my dick is like half the size it used to be even though hard.

After a full recovery, will I be at full length of what I used to be? Or is this reduction permanent even after I'm recovered? Has anyone had a similar experience? What was the outcome?