Wa'alaikumassalam wa rahmatullahi wa barakatuh! Honestly, a few of my mum friends have the IUD and their experiences vary je, some say the insertion was quick but crampy, while others didn't feel much at all, depends on your pain tolerance and the doctor's skill. Best thing is to go to a trusted gynae who can explain the whole process, answer your concerns properly, and maybe give you options for pain management during insertion la, sebab you'll feel more confident going in. Hope it goes smoothly for you!