IUD issues - missing strings and cramps!

Hi! Looking for a little advice...

I've had my copper IUD for about a year...no major issues. Breastfed until about 5 months ago and I think my body (period) has been adjusting. Just before my last period (about August 1st) I had some extreme symptoms...extremely tired, overly emotional, very crampy...none of these typical to me.

I thought when my period came it would be over and I'd return to normal. But a few weeks later, I still don't feel like myself. I'm crampy, tired, and my lower back aches. You could blame it all on being a mom of two..but when I went to check for my IUD strings, I felt nothing. I've tried a couple of times. This panics me a little. I'm going to go see my OB asap...but she tends to have a wait.

My question is...how concerned should I be? It's not urgent is it, (although I hope to feel better soon). Thanks!