my spine is extremely hypermobile, i can do all the tricks the contortionists in the circus do and several consultants have commented that they've never seen anyone with a back as flexible as mine
i get a lot of crunching too, and also the same feeling of relief when i can get an achy bit of back to crack. i find the stronger i keep the muscles in my back, the less my back hurts although it still cracks as much. you can also feel all my vertebrae moving by pressing them, this is also possible in 'normal' (non bendy) people but it is unusual to be able to move every bone and unusual to move them the amount that they move in us bendy people as our soft tissues allow a greater range of movement from each bone.
lots of my back pain comes from tightened up mucles and so stretching eases it really well, i have a gym ball and find it really nice to wedge it against the sofa (to stabilise it a little) and then arch over it and place my hands on the floor so i dont fall, it's a really nice stretch! and i find swimming a really good way to keep my back muscles strong while relieving the pain a little (i always hurt less in the water, as your weight is supported so your back muscles get a bit of a break while you're just bobbing around). pilates is also fab and has made a huge difference to the pain i feel in my lower back and the pain i get a bra-strap level in my upper back.
i also had a few courses of acupuncture on the nhs from my local pain clinic and it worked really well at easing the crampy pain that i get in my upper back.
generally keeping moving also seems to limit my back pain, the longer i sit still the more my back muscles cramp up so i fidget, wiggle, and move my back when i'm sitting down.
so you're definately not alone!