Is it normal to feel emotional after sex?

I’ve been seeing someone for about a year now and, I have to admit thing have changed. I’m starting to second guess myself and wonder if I truly want to continue the relationship. Sex has always been great until recently it just doesn’t feel the same... there’s no communication or passion. After today for some odd reason after we had sex I felt super sad to the point where I wanted to actually cry. Is that normal ? Why did I feel so upset ? Has anyone else felt this way?