It is ok that your back “cracks”, but please do not force your spine to “crack”. Imagine that your spine is like a dog attached to a chain in the yard. The dog will try to move around the yard in any way that it can. This means it will pull the chain in any manner that it can.
If there are any links in the chain that are stuck or can not function properly, the other links take on the stress of the pulling from the dog. This additional stress on the other links can create them to breakdown and possibly make the chain fail.
The pulling of the chain by the dog is the force that people put on to their spine to get it to “crack”. Please allow a chiropractor to restore the proper function of your spine and therefore not allow your spine to fail like the chain.