level

Until last week I used to have Level 50 on survival, however, now I have Level 8. Can someone explain this to me or please fix it. Here are screenshots of before and now. Before: Now:

Just a simple question, I've used a command a few days ago (someone said it in global chat) which shows you the value of the block you are currently holding. The value that it might add to your /is level that is. Now, I don't remember what the command was, and would like to know it. Does anyone...