If there is no pain or cracking or 'catch' when you chew or open and close your jaw, then there is unlikely to be anything wrong with your jaw itself.
If you do have pain, then it is possible that are have an inflammation of the tempomandibular joint (often called "TMJ"). This is a chronic condition that both your dentist
and your primary care doctor
can give you some advice on how to treat. Typical treatments include pain relievers, physical therapy, oral splinting and, in more severe cases, surgery.
In the case of no pain, then the most likely thing that is going on is that you are having some crowding in the mouth, or some related condition, which is slowly causing migration of the teeth over time. This is a very common problem which can often creep up on you because the changes in your bite pattern happen slowly over years. I would recommend that you go to see your dentist about this problem; they will be able to confirm whether or not a problem with your teeth is causing this change; if so, they may decide to refer you to an orthodontist
to determine if treatment is possible or necessary.