Back pain. What should i avoid doing?

Male 21 , height : 5"8 weight 80kg. India Hello, i am having back pain in my thoracic region since 2 years..some blood tests by my orthopedist I don't know the names but i can tell the names of factors written on the tests(uric acid, rheumatoid factor , cbc, crp , esr, hlab 27) were done all were normal, hlab 27 was negative , xray was normal too and was the MRI.No change in the pain. I joined physiotherapy , they didn't find any abnormalities in my back , did it for 2 months the pain got less but it never vanished. Electro therapy didn't work they just did it for 2 days and then stopped. The pain got decreased since i started the physiotherapy but it dropped to a certain point and stopped also whenever i used to get up in the morning it was difficult for me to relax my spine, i had to stay upright for few mins/hours this thing got decreased after the physiotherapy but again never vanished. What could be the cause? What should I avoid doing? I have stopped physiotherapy as of now.