IUD expelling

So earlier this evening I started to bleed heavily and cramp. When I went to the bathroom my Mirena IUD came out. I had it in for 5 weeks. I will go to the doctor on Monday. But does anyone know if I get another put in right away what the chances of this happening again are? And if this has happened to you did the second one stay in place or did you choose another form of birth control?

I am aware to use a back up birth control until I go to the doctor. I also took a pregnancy test and it was negative.