Apart from what my colleague just told you, you should try and reduce your weight which has overall effect on your whole spine. Dr vijay Ramnani MCSP  (London )

It's likely to be lumbo-sacral joint dysfunction. This is the joint where our spine and hip joints connect and our body weight is transferred from upper to lower part. A variety of reasons like strain, laxity of the ligament​, positional fault, posture changes etc can contribute.. please get yourself evaluated by a physiotherapist who can assess and give you therapeutic exercises. After this you may be given posture correction tips which will help in recurrence of the condition.