A.H.
You don't mention which IUD you have. I have the Mirena and mine has been wonderful. I would worry a lot about those symptoms. I got mine in 5/06 and I bled a little irregulary the first couple of months and from then on I don't have anything but maybe slight spotting. My PMS might be a little more than before, but I think it seems worse during months I am more stressed so it could just be that.
I would worry that your doc just sends you home with no explanation. I think I would get the second just based on that.
I hope it gets better for you.
Good luck!