I had my implant done in August 2010. I was in hospital for 2 nights but I dont remember the pain being as bad as you describe. Ive had spinal fusions and other back surgeries and I will say they were HORRENDOUS, but when I had both my trial and permanent implant the pain I had after both procedures definitely werent as bad as the surgeries I had previously.
I remember the area around the battery, which is in my left butt , was extremely painful but that did subside after about a week. I didnt like the sensation of the actual battery protruding through my skin but thats something that Ive gotten used to over the past couple of years.
I do hope that your pain will subside and that things will settle down for you very very soon