If is possible you got some adware on your system, and it is busy using your system to generate clicks on ads to increase someone ad revenue.
The EtreCheck output Eric Root suggested, if posted as a reply to this thread, would allow the forum to analyze it for you, plus EtreCheck does recognize some forms of adware. NOTE: It is best to allow your system to run for awhile with all its problems so that EtreCheck will have useful information to collect. If you run it shortly after booting, all the valuable information and statistics will not have been generated yet.
There is also MalwareBytes that does a good job with adware removal.
<https://www.malwarebytes.org/>
So I would post EtreCheck output to get the forum community helping while you work your way through some of the other links Eric has provided.