I've had a copper IUD in place for 30 months (since ds was 9 weeks old.) He breastfed until he was 27 months with no problems. I have any supply problems. I did get my periods back immediately following insertion. They were ridiculously heavy for 9 months. They were so heavy, I was getting up about every 2 hours in the night to change a super plus tampon. Then after about 9 months, it tapered off and my periods returned to normal.
My IUD was painful for insertion and for a couple of days afterward I had quite a bit og cramping, but nothing I couldn't handle. Your body tries to expel the IUD, so your uterus will contract. The OBGYN who inserted it cut the strings very short to avoid discomfort for my dh. I noticed during the first year that I couldn't feel the strings. I had an x-ray which determined the IUD was still in place, but the strings are nowhere to be found.
I just went back today to the OBGYN to have it removed and she had to try to find the strings by "fishing around" up there as she put it. It was painful, but unsuccessful. So I will be heading to the OR for removal under general anaesthetic.
So while I didn't have any problems with Bfing, and dh has never been uncomfortable, I am having some troubles with removal.
There is always a risk that the IUD will come out. You should check monthly to feel the strings to make sure it is still in place. (How I discoved my strings were gone, up into my cervix.)
Overall, I'm happy I got an IUD, no problems until now.