Happened so many times...
Feeling pregnant even though I'm not has happened to me a ton of times, especially before I'd had a confirmed pregnancy so I wasn't sure exactly what pregnancy symptoms would feel like, just a list to go off.
In the days when my period became irregular, then switched to that approx. 6 week cycle, in weeks 4-6 I was constantly thinking I was pregnant. I would in turn get nauseous, I had sore boobs (PMS I guess), weird skin, the works.
The mind is a powerful thing.