i keep getting a message that safari can't establish a secure connection

Does this happen with credible sites such as Google or Apple? If you are visiting other unreliable websites, then Safari may actually be unable to establish a secure connection. See If Safari says it can't establish a secure connection, or the website is using weak encryption - Apple Support.

If this is happening on credible websites however, it might have something to do with your anti-virus. Do you have Avast anti-virus installed? Apparently this can cause Safari to say that it can't establish a secure connection and can be resolved by disabling your Web Shield in Avast.

Some other tests to try.

Try setting up another admin user account to see if the same problem continues. Please post back on whether or not this worked. Also try the Safe Mode. Please post back on whether or not this worked.

Isolating an issue by using another user account 

Safe Mode - About

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

Etrecheck – System Information

If the log won’t post, try posting it in Pastebin and provide a link in a reply        Pastebin