I’d use a “Search and Replace” plugin (I like “Better Search and Replace”) to search for all http://www.example.com and replace with https://www.example.com . That will fix media URLs, for instance, and other settings.
It could also be that your theme is calling http resources rather than https. You could look in the Developer screen (F12 in your browser usually) at the Network tab to see what http (vs https) resources are being loaded, and use that info to find the source code that is using http instead of https.
Backup your database first, of course, although I’ve had no problems with the “Better Search and Replace” plugin.