Instant mood change?

My husband and I have been thriving lately. We just got back from a 7 day cruise and he doesn’t go back to work until tomorrow and I’m loving it! (He works 24 hr shifts so we don’t have a whole lot of time together). But with all the time we’ve been spending together, we haven’t fought or gotten irritated with each other. Tonight, it’s almost like I felt a switch go off in my brain. All of a sudden I got really irritated with him (not mad or anything just super irritable very quickly). I mean I know this happens to everyone, but this time I could feel it coming. Is that normal? I’m not PMSing but there’s a good chance I could be in the very early stages of pregnancy