I keep getting emails and on my phone it's saying that there's more devices than I have, I only have a iPhone and that's it

Not sure what you mean by "logged into devices" but if you mean devices logged into iCloud, go to Settings, tap on your Apple ID and a little way down you should see a list of devices that are linked to your iCloud account. So in your case that should just be your phone. If you see other devices then there certainly is an issue. But I suspect that the emails are just scams.