Back Problem - 17yo Male

Hey, i'm new to the forums, looking to get some feedback on my problem.

I'm only 17 years old and have been suffering from back pain for the last couple of years. I've taken an x-ray which according to my physical therapist, is perfectly fine, he said my spine was in normal allignment and showed no abnormalities. I've also taken an mri, which they also said was for the most part fine, that one of my discs was 'very slightly off' but should be fixed with a little therapy. I've never had any leg numbness or pain in relation to my back.

With that said, my problem is my lower back. I guess you can say i've 'thrown it out' a few times to the point where I can't do much more than just stand straight up or lay down. Any movement to arch my back or bend down would cause a very stabbing pain in my back. The strange thing is that I used to have random back aches that lasted for 5-10 minutes, where my back was in agonizing pain but then it would just go away completely afterwards. That hasn't happened in a while, now I just have slight to extreme discomfort in my back.

It varies from time to time, like i'll go a few days where a specific spot of my lower left back hurts when I make any spinal movment, and some days/weeks where my other side hurts. Even when lifting lets say an object weighing 15-20 lbs, while im leaning over, a new stabbing backpain will come out of nowhere and will hurt anywhere from 5 days to a few weeks.

I've tried to put up with it for as long as possible, hoping it would recover by its own, and have restricted myself from doing anything that can be hazardous to my back or lifting anything heavy, but it hasn't worked.

One of the things that has completely shocked me is that during summer vacation, I was out of the country for two weeks. In those two weeks my back recovered 200% and I felt better than ever. I didn't know what it was, seeing as how during those weeks I did more running around and lifting than I would do at home in months. Within a month of getting back my back pain started again, but I couldn't put my finger on what the problem could be untill just recently. My grandma from out of town came to visit and she borrowed my bedroom to sleep in. She stayed for about 9 days and in those 9 days I slept on the floor with only a few blankets of cushion. By the time she left my back was feel a lot better than 9 days before.

Heres my question, could it really be the bed causing the problem? I'm trying to put this to the test and am sleeping on the ground for the next week, to see if my back improves. Any suggestions/comments/advice would be greatly appreciated.