It's not often recognized but having a large stomach / gut also puts stress on the lower back.
I hurt my lower back over exerting in the gym and saw a chiropractor for over a year until it fully healed but lower back issues ain't no joke.
I will share a secret of what I use. A lot of body builders use this as well and I will tell you it works almost instantly. My Chiropractor couldn't professionally tell me it's ok to use but off the record he recognized that it works and is potent. It's like a bio-freeze for horses with sore muscles called Absorbine / Horse Liniment. I know you can find at Tractor Supply Co. they may also sell it at Pets Mart.