ESET offers a free offline scan of your computer for viruses and malware. It is currently doing a scan of my computer as I type this. If you'd like to try it, you can download the scan module here. You answer a few questions about the scan, then click start. You can continue to use your computer while it completes the scan, and it works on a PC or Mac.
It has currently scanned 130,000 files on my computer -- and is about half done -- and hasn't found anything yet -- and hopefully it won't. Of course ESET offers a paid version, which they hope you will eventually buy, but you don't have to in order to get the scan. Here is an article describing other virus scanning programs you might consider trying.
If you're running Windows 10 on a PC, here is an article you might read using Windows Defender offline to do a virus scan. I have not tried this one yet, but plan to read more about it.