My experience getting Mirena inserted

I just had the mirena IUD inserted for the first time (my first IUD). I have two kids, the youngest is 7 months. I told my OB I was so scared to have it inserted and I was so nervous, etc. she said "you've had two kids, this is nothing" .... The procedure was highly uncomfortable but was not super painful - the actual insertion was the most painful part but wasn't too bad. The nurse charted my pain reaction to the insertion as a 2 and was laughing jokingly at my reaction because I was so unsure about the whole thing and she had had 2 mirenas (and no kids) and her IUD insertions apparently weren't bad. 
THEN as soon as it was finished I immediately started having cramps which started to get bad after about 5 minutes and progressively got worse.  It's been an hour since the procedure finished and the cramps are SO aweful 😫 it hurts from my belly button all the way down to my knees! Aghhhh but it's going to be worth it, right? No more babies for 5 years! 
I read prior to my appointment the insertion is the worst part and there's some mild cramping after. Nope. Not what happened! The insertion was pretty quick (10 minutes) and not so bad, but the cramps afterwords are SO strong and painful!! 
How long will these cramps last? My doctor said a couple days but the first day is the worst and it should get better pretty quick.