My rings stopped fitting overnight!

I'm only 18+2. My blood pressure has been fine. My rings have been a little snug and difficult to put on in the morning but today I absolutely could not get even one on :(. I feel so naked! My blood pressure is good. I have been gaining weight more quickly than I should, but I wouldn't think that'd make such a difference over night. Maybe I'm retaining water? I guess I'll cut out salt and see what happens.