I think my computer and password protected accounts have been hacked. Is there any way to confirm my suspicions?

I'm currently going through a legal issue with my ex. Since he began this legal thing, when I select my email address, my ex's name comes up. He's never used this email, nor has he ever used this computer. Also I did a search for him, and his contact information is the city I live in. He lives in another state. Recently I was accessing my digital car loan info in a folder titled "Honda" in my email. As I attempted to open the file, it disappeared right before my eyes. It wasn't in the trash either. Contents in folders associated to our divorce have all been deleted. Is there any trick I can use to find out? A couple of years ago I found out he was accessing my information - I think by key stroke. He captured messages between me and a friend who was having marital problems. He copied all the messages on FB messenger and sent them to her husband in an email. What was really puzzling is that we had an agreement to deleted each message as soon as it was read or sent. I know I did, I'm certain my friend did. Is there some way to confirm my suspicions?

You need a restraining order, at least. Me, I'd probably move to another city and not tell anybody where.

Get your PC cleaned by a professional (with a detailed report of ANYTHING they find) and after that, change all your passwords.

Accessing someone elses information like this is illegal, and could be a felony in your area.