Back pain. maybe a nerve issue in spine.

See... there's this issue I in my back...I feel sudden jerk...sudden pain...so high that I have to sit immediately wherever I can...and slowly do some stretches to cure the pain completely.....this happens not so frequently...but when it does...it's very high and severe...this is the issue with my spine...maybe of nerve maybe of bone...but I had my X-Ray report done and it shows no problem with bone..so...this pain is maybe due to nerve blocking or something like this...I don't know...this is happening for 3 4 years...I'm in college right now...and in 10th standard I fell on ground on my back...from a 10-12 feet tall wall....after that incident these type of issues are common with me...so...I just wanna find out what is it...and how to cure it. I've attached my X- Ray...in case you wanna check my bone status of spine...it usually happens in lumber region...but from a week or so...I got some attacks of this pain in thoracic region also.