Burning sensation in upper back ,

Hello doctor, myself ranjith from tamilnadu Last 2019 February I have burning sensation all over my body I went many doctors they took all blood test urine test and said nothing again I see one doctor he said you have sigmoid colitis like that later I went to gem hospital, Coimbatore (gastroenterology specialist hospital) they also took blood test,sigmoidoscopy, ULTRASOUND SCAN they said everything is normal like that.again few months later I have burning sensation problem especially upper body, genital also so heat,again I went to gem hospital they said no gastroenterology problem they said psychological related conditions so I went to psychiatrist he said u have OCD so take sertraline tablet and take clonotril if needed But burning sensation come and go occasionally less time only I have confusion whether it is psychological problem or neurology problem or some doctors suggest vitamin deficiency.please suggest me  doctor what I have to do. Now iam taking sertraline 150-200mg tablet