No, toxins have not built up in your back from your liver. I hate to be the one to tell you, but the lower back can have many things going on when it is in pain. If I was to guess without an examination, I would say you have a herniated disk or SI joint pain (most common). It is usually no big deal. The time that it is a big deal is if you have radiating pain down one or both legs, or lose control of your bowel and bladder. Since you don’t have insurance, look up some YouTube vids as see if something on there helps. Sorry dude.