I'm 23 years old and I have always cracked and popped my joints (knuckles, ankles, toes, back) but recently I've been having to crack my back excessively.... There is no real pain to this, only an extremely uncomfortable tightness that is only alleviated by cracking my back. It's gotten to many many times daily, as in 50+. But when I do crack my back, there is almost always an audible pop. And if I stretch and crack my back, I'll have to do it all over again in a few minutes because the tightness returns.
I have not sought out any doctors for this yet. Although I have seen a chiropractor in the past and I do have uneven legs (and I wear an insole for that everyday) as well as a curved spine.