Apple ID Sign-In

I got a message on my phone yesterday that someone had signed in to a new Macbook Pro with my apple-ID. Then this morning, I got the same message on my IMAC when I opened it.

I have a macbook pro on my account. But I haven't turned it on lately.

Only all my own devices are showing up when I check my devices on my apple ID.

Is this a situation where my apple ID could be stolen and being used elsewhere? If so, would the device show up on my sign on page.

Since I haven't turned on my macbook pro in quite some time, I'm sure the message can't be about that one.

Any insight into this situation would be much appreciated.

Thank you.