Emails disappear/ Amazon login codes.

I have had several problems in the past week. Emails disappear and sometimes return sometimes don't. They are not in any other folders. Its very erratic and not predictable. I also was not receiving any emails for a couple days. Now I occasionally receive one from a few days ago. I also have started receiving Amazon emails with codes to login. I know this is a scam and have not logged in. It happens on any computer I try to log in to and don't know how they are related. How do I fix this? I have not changed any settings recently.