If the sex is unbelievable, compare it to a God you don't believe in.
I'm southern, god speak litters the common vernacular. I no more expect flames flying out my ass when I say, "shit fire & save the matches " than I do divine intervention when I say "oh gawd" .
No problem saying god in any context. Why would one unless one thinks it’s blasphemy?
Doesn't bother mew at all.
In fact I consider it an accomplishment when I can get my atheist partner to actually scream "Jesus CHRIST!", because while "oh god" or "ohFuckOhFuckOhFuck" are fairly common, that's special.
I'm gong to start saying Oh Boy! (I just saw The Long Shot movie)
So when you say "fuck me" do you actually do it? Just kidding, the terms oh my god, jesus christ and the like are just that, expressions, expletives, use them at your leisure, and don't feel bad about it, unless you believe that by saying jesus h christ you will suddenly be converted into a raving bible thumper.
I prefer to scream 'oh my PASTA! Praise MEATBALLS!"