IUD-mirena

My obgyn has recommended either an iud or the bar in my arm for birth control because the pills simply aren't working for me. I bleed all month long and have tried dozens of brands. I heard not to get an iud until after you've had a child.. Is there anyone who has never been pregnant, had an iud and still been able to conceive afterwards? I don't think my dr would steer me wrong but I'm still nervous. Any advise?