Oooh dear, nasty. I'd take the course of anti-biotics first, and see if the pain and/or swelling goes down pink, because after an x-ray, you might need to have the remains of the teeth extracted, which they won't do whilst an abscess's present.
I agree with lil. The pus usually forms around the root area, so the crowns were probably put on whilst there was an infection already there. If the anti-biotics don't work, then at the very least I expect you'll have to have the crowns re-done after treatment of the roots. Urgh...best of luck hun. x