A week seems like a long time, and if you are feeling worse, I’d go. Better safe than sorry. If you prefer the care at the other ER and don’t mind the extra drive, then I’d go there. I think feeling comfortable with the hospital that is giving you care is important. Aside from the fact that it is a Sunday and you might not want to wait until tomorrow to see your GP, is there anything else that leads you think this might be an emergency? If you have other concerns, you might want to skip and go to the ER that is closer.