Switching Birth Control. Is the IUD a good choice

Meredith
I'm looking to switch birth control. Currently I've been taking the pill for the last 2 years. I tried the Nuvaring for about 2 months and was constantly bleeding for about 6 weeks. 
The IUD is something I want to switch to. I have heard some negative symptoms about it. Do IUD's hurt at all? Have you gained weight or have you had bad mood swings?
I was hoping some of you had some answers or would share your experience with me.
Thanks