Pigmented lesions /Nevus Of Ota on face.

Hi All, In last 1.5 year I have got pigments on only left half of my face. I just had only 5-10 pigments on fore head when I was around 10 yrs old. But suddenly in last 1.5 years these have rapidly grown covering almost complete left half of my face. I have consulted many doctors and they have suggested me to go for Q switch ND yag laser treatment and said this is kind of nevus Of Ota. But no one can explain me the reason of this sudden increase and the size of the pigments has been increasing regularly. I have tried using depigmentation cream given by doctors but nothing has worked. Can anyone please help me with the best laser machine and place to go for the treatment without any side effects. I am lot worried about any side effects I have attached my picture for reference. Appreciate your help.