I used to have terrible lower back pain and my dad told me to stretch and work on my core strength. I was actually shocked how quickly it got better. One of my teammates started to get bad back pain a few months later; she went to a physiotherapist and he gave her a stretching/core routine to do at home. :p

The best long-term treatment is to stay strong and fit, maintain a healthy weight, and focus on correct posture to avoid creating further problems.

In the meantime, you can always take medication or try a heating or cooling pack (or alternate between the two).

If it continues or gets worse be sure to see a professional.

Do back excersizes. I had the same problem and usually it's either linked to back tension or a compressed spinal collumn.
The thing that I do is lay on my back and turn my upper body until it cracks then go the other way, it generally relieves a lot of pressure

massages

Basically this. I have terrible back pains, have had them all my life. I went to a Physiotherapist and he worked on my back and gave me exercises to strengthen my core and it really does help incredibly. There are loads of tutorials online that you can look at to strengthen your back. If it gets extremely bad, I would suggest visiting a Physiotherapist, because he/she will give you loads of exercises especially for you and whatever problem you may have.
I would also take a look at your footwear because you can get very bad back pain from bad shoes, especially if you have fallen arches then it will cause allot of pain. So have a look and see if you do have fallen arches then you can get insoles to try and fix it.

Also make sure to keep an eye of your posture whilst walking as well as sitting. Bad posture is a downward spiral because your body typically compensates for bad posture with worsening posture. Being aware of your posture, straightening your back, lifting your chest, rolling your shoulders back and rotating your pelvis so your stomach and behind are tucked in will help improve your posture. Unless posture is part of your sport or exercise, if you're like most people, you will have a hard time being consistent with it. Footwear can play a role like Kopite said, so you may want to look at that. Also, maybe the mattress you sleep on is too soft or hard. I know it's not the cheapest solution, but a memory foam mattress could help with the pain (and the extra comfort is a bonus).

if these have been going on for weeks now youre going to want to rule out sculosis and disk problems, since it is the lumbar a disk problem is likely than say thoratic. but its probably nothing a good stretch, massage and motrin wont fix.

see a doctor

you can determine whether or not you have a serious back issue without first seeing a doctor, just google your symptoms and you have cancer

I had some similar problems, that's why I can help you.You just need to get some Posture corerctors for men that will erase any back pain that you have. I believe that it can be an amazing solution to your problems.