someone accessed my account on their device

My ex boyfriend knew my apple ID and I think he got into my account - from what I can tell he has deleted himself from my contacts - I'm not sure what else he did. I did get an email from apple saying my apple ID was used to sign in to icloud via a web browser - definitely not me. The second time he did it I got no notification. Is there any way of finding out where the web browser was? we live in different states, so I thought this would prove it. I just want to know.