I felt exactly the same when I was an NQT+1. You are not alone! I am 4 years after my NQT year with currciulum reponsibilty and still feel somedays that I am paddling to stay afloat ( I think that's the expression). The only difference is I now have more knowledge of coping strategies in place to help me get through (increased peer marking, self assessment tecniques etc). I also work in a Catholic school and although I am not the coordinator I know there are a plethora of websites out there - don't spend ages searching but is there something you can adapt? Also, how was your relationship with your mentor or do you have someone else in school you can have a chat with? Perhaps your SLT might be able to find you a little one off time for some RE work?