Pain in the back

My back was so painful when I tried to get up.
Last night, when I was teaching English to students and just seated still, I felt an acute pain in my back. Since then it has got worse.
A back problem is not easy to understand logically or clearly. It comes all of a sudden without any sign or cause that rings even a distant bell. It also goes without any reason.
Today, I was supposed to attend a meeting at Kyoto University and planned to visit some autumnal places there afterward. But I canceled the meeting. I have no choice but lying on the bed all day long. Not bad.