Thank you both, I was able to find that my monthly scan was running daily and deleted it. I don't know why it suddenly started running every day. I've been using Avast for over 20 years and am normally quite satisfied with it since it normally does its job without me having to do anything at all.
When I first decided to ask about the problem, the monthly scan was set to run on the 10th of every month, the day before my original post. When I looked at it the next day, it was set to run on the 11th. The following day, it was set to run on the 12th. Basically, each day for four days, the scan showed that it was set to run the day before. This scan issue has been frustrating me for almost a month so I'm hoping that I have fixed the problem.