Back pain from last 20 days help me.

I have a back Pain ! 20 days back I lift weights in my home for cleaning! After that sudden I have ache In my back I barely move I use zerodol MR once a day for 3 days -4days that actue pain go away. But there was a pain when I was sitting or doing something .. I went to orthopedic doctor and describe him everything he told it's a muscle spasm and it will go away he gave me Thickoren 4 table to use twice a day for 10 days and pain oil relief and streching  exersise as I used it for 10 days there was less pain pain subside. But now it's been 20 days I am not using any medication but when I sit somewhere for 30 min my pain is still persist.. I am working and sitting for 5-6 hours and I usually move in between that is not a concern but I don't know why this pain is not going please help me how can I get relief from this . If it can go with excercise will do .. help me is there is any solution.