Should I go to the er?

For the past 2-3 days I have had really bad stomach pains. It gets worse day by day. It hurts to walk, sit, and use the bathroom.(pee & poop) When I push on my stomach it hurts really bad. The pain is starting to go to my back. I’ll be 3 weeks pp tomorrow via c section. I don’t know if I should call the on call nurse or just go to er? Any advice will be appreciated. Thanks!