Hey there Aimee_Phillips19,
Thanks for reaching out to Apple Support Communities. I understand you’re having an issue with your Activity history. I’ll be happy to help with this.
If previous workouts and closed rings are disappearing, I would force close the Activity app on your iPhone:
How to force an app to close on your iPhone, iPad, or iPod touch
Then restart it and your Apple Watch:
Restart your iPhone
How to restart your Apple Watch
Check your Activity history once more and see if the issue is resolved:
Track daily activity with Apple Watch
If you still have issues, go through the steps under Get help from the following article:
Earn Activity awards using your Apple Watch
Regards.