I'll take a stab in the dark and say you've been hacked. There are some rather nasty bits of Malware that regular programs don't detect. You can fall into a false sense of security when you get a clean bill of health. If you're familiar with what processes you're meant to have in task manager, you might be able to see something.
Open up task manager, select to see processes from all users and see if you have dllhost running. If it is, how many instances are there and how much CPU are they using. The virus that attaches itself to that is one of the ones causing most of the issues at the moment as far as hacking goes. Most of the time it comes from dodgy emails, but I know of a few people who have got it just by visiting websites.
Most antimalware programs won't detect it. One of the Norton programs does detect it, but can't get rid of it. This thing just runs in the background sending absolutely everything you do to somewhere in Russia. I would suggest at the moment, until you can find out for sure if you do have malware, change your passwords using your phone that is disconnected from your home network.
If your dllhost process is using more than 15% CPU, let me know and I'll tell you how to get rid of it.
