Re: Back pain, no idea what to do.
The area you have circled is the lower end of the lumbar segment of the spine where it goes into the sacrum. The L5-S1 segment, along with the one above it, L4-L5, get the most wear-and-tear of all the spinal segments due to
absorbing the brunt of all spinal movement. The spine is able to bend at all levels, but is perhaps most flexible and also able to twist the most at these two levels.
It may be that you have a disc at this level that is bulging, or there may be some stenosis at this level. Most people develop stenosis to some degree as they age. Very simply put, stenosis is a narrowing which can result in a nerve getting "pinched."
Stenosis in this area is generally relieved when the person leans forward slightly, like when pushing a grocery cart, and often feels worse when the patient lies flat or does something that causes the back to arch backward. When the nerve is badly irritated, pain will run down into the leg, sometimes to the toes. When the body is positioned in such a way as to "release" the nerve, the pain stops. As the disc degenerates, pain will get worse and the times when the pain stops are few and far between.
This is one of the more common things it could be. It could also be some sort of muscular issue or even one of the fascia and soft tissue pulling in such a way as to effect the nerves.
It could also be a problem with the sacroiliac joints that are located directly beneath the sacrum. SI joint pain can mimic the symptoms of a lower lumbar disc issue.
These are the most common problems I can think of at the moment. I'm sure there are other things that could be causing your pain. There's a lot going on in that area with many nerves running through the area. It is where the nerves of the cauda equina separate and branch into the sciatic nerve which runs down the back of each leg.
If the pain persists, you may want to consult with your doctor. If you look up lower back pain, you will find much information as it is a common health complaint.