My husband got a vasectomy and now Im worried?

My husband had a vasectomy on 9-4-09, he has stayed on the couch for a little under 2 weeks and he is back to work for the first time and he is still in alot of pain. Now there saying that they need to go in and do an ultra sound i am really worried, I am really worried that something might be wrong. If any one can tell me if they have gone through this and what the outcome was that would be great. Thank you for the help.