My mirena insertion wasnt pleasant either. The dr had to insert it twice since the iud didnt seat properly the first time. Felt like a really bad cramp and my cervix was painful for a day or two.
My first iud was inserted 4 months postpartum and I didnt feel a thing. Not so lucky the second time. And I even took advil before.
Good luck with the iud. Hope you have great success like i have.