Can I see who has signed in to my account and what device was signed in

Karrie78 wrote:

where can I find who’s been on my account?

You can only find out if they have logged in presently, not if they have logged out.

Settings > [Tap your Name} > Device will appear here...

See the pic below

All those with whom you have shared your Apple ID and Passwords can sign into your account thus making your data on your iPhone vulnerable.