Soreness in the back that is made better when you lay flat is something that we treat in our office on a regular basis. These symptoms are often caused by restrictions in the joints in the spine. This is best treated with a chiropractic adjustment. After an examination, the chiropractor will determine if an adjustment is the best treatment option. Seeing a chiropractor is the best place to get started with resolving this issue. IF you do not have a chiropractor, here is a map of evidence-based chiropractors around the world. http://www.forwardthinkingchiro.com/member-map-1/#!map
See the video titled "The Chiropractor's Role" here:
Hope I helped. Got your back.
Dr. Todd Gewant
Dr. Sonal Dalal, DC
Based on what you are describing it sounds like a lack of core balance and tight hip flexors which stretch out when you are laying on a harder support like the ground.
We focus on fixing that by stretching, then strengthening and stabilizing the surrounding tissues of the lumbar joints after an adjustment.
Check out our facebook page for tips and tricks you can do with stretching and to set up an appointment call 507-337-2423 as the purpose of that first visit is to make sure we can help!