thanx for sharing your concern,
loose tooth means you have localized periodontitis
that means infection in your attachment apparatus of the jaw .
this infection causes pain, bleeding, pocket. and mobility of teeth.
tooth becomes mobile due to surrounding bone loss to which it is anchored.
if timely care is not taken then tooth becomes mobile and finally falls off .
it is infectious too. as it involves many bacterias therefore.
i would suggest you to visit your dentist
in the early stages and get OPG done. this would help you to check the amount of bone loss and infection in other teeths too.
it can be cured by deep scaling,root plaining, curettage and flap surgery.
remember periodontal pathology requires treatment as well as maintenance therapy.
you are adviced to maintain regular brushing , flossing , mouth rinsing with antiseptic solution.
hope this helps take care