SLOW...but never before

Well, it started about a month or so ago.  As if on the turn of dime, my computer became sooo slow and remains that way.  My interent connection is fast (88 Mbps download and 12 Mbps uplaod) but my computer suddenly can't seem to manage aything that doesn't look like dial up.  I have MalwareBytes and have run several other scans, nothing shows.  I am aware that I don't have enough RAM, however, that doesn't account for the sudden change.  Any help would be appreciated.

Further update - the problem may be a bit deeper?  I can log onto the computer (no issues) but once a webpage is open (home page), no other page will follow.  The home page is yahoo - all mail functions work, and the news stories stream fine…but when any external links are clicked, they will open a new tab and get timed out.