Well, I have back pain since average one year. A month ago, I prayed for it, asking God to heal me, and I posted a prayer request on the C28 prayer board. The next day, my pain was gone, but I felt very ashamed, because I sinned the same day (knowing it was a sin while doing it). God healed me, and all I've done to thank him was sinning, I was so ashamed. So, I asked him to let my back-pain when I make a sin.
From this day, whenever I sin and don't repent myself, I have a horrible back pain the next day, and when I repent myself, asking for forgiveness, then the pain leave within the five following minutes. This is awesome, and helps me to follow God"s will instead of my will :-)
Sorry if there is mistakes, I live in Switzerland and don't speak french ;-)