What Causes Severe Abdominal Cramping Along With Vaginal Spotting While On IUD?

I have been having severe cramping and brown spotting. I decided to check my IUD strings and I discovered that the strings are now 1/2 an inch from the opening of my vagina. Does this mean it has expelled? I have had the IUD for a year and a few months now. Still have a regular period, most things are normal other than this new development.