I used to go to the gym after which i started having a lower back pain, turns out my back is strained. this has been my condition since last 7 months.

Consider testing: A back strain is somewhat of a generic term that implies you have injured a muscle in the back. But if you are having back pain that is lasting 7 months, it almost certainly more than a simple syrai. Consider getting an MRI to further diagnose the cause of your problem. Thank you for your question.

Get Xrays: It is very uncommon for a 19 year old to have a back strain for 7 months. You should be seen and evaluated for a possible stress fracture of your low back (spondylolysis). Xrays should be able to identify this and if not advanced imaging (ct or mri) will make the diagnosis if clinical exam is suggestive (pain with hyper extension etc.).