Mike has given you wise advice. Another I offer is that if the computer has been running more than a week without restarting, try a restart. That cleans a lot of "deadwood" from caches and log files and does some system checks.
If those steps do not help, please consider the following:
Slowdowns after a system version update are often software-related, commonly caused by unneeded anti-virus software and so-called "cleaning/tune-up" apps. To help us determine if this is a software conflict, please post a snapshot of your system configuration. Fortunately there is a safe and secure way to do that.
A respected and long-serving member of these communities has created a simple utility that will take that "snapshot" of your configuration without revealing any sensitive information about you and your computer. It only runs when you tell it to, not in the background, and therefore creates no performance penalties. It is Etrecheck, and is available here:
http://etrecheck.com/
Run it and, when its results display, select "Report" from the left-hand pane (scroll down to teh bottom), then click Etrecheck's "Share Report" icon followed by "Copy Report" from the resulting dropdown. Paste the entire report into a response to your own thread here. It will often allow us to quickly identify or eliminate software as the problem.
If you have a rotational hard drive, long load times can herald a hard drive failure. The Etrecheck runtime that is included in the report can help us tell if that tis the case.
