Welcome to [words=http://www.mattersofsize.com/join-now.html]MOS[/words]! Getting an accurate measurement almost requires an 'assistant' (I prefer slender/curvy dark-haired ones for this

)...holding an iPhone/ruler/cock all while trying to maintain the highest possible EQ is truly a feat! (then you can add 'ruler-phobia' to compound the angst, lol).
I don't think you lose size as you age, but other variables can come into-play, i.e.
weight gain, EQ,
weight gain

Spend some time reading through the forums and develop a plan that fits your goals as well as lifestyle...you'll be amazed at the initial signs of gains.