Site serving up http and https

Hi,
Im hoping someone can help shed some light on this or provide a solution.

I’m running wordpress 4.6 for my blog photography.news and have never had or used a secure certificate. Therefore the site should all be http. However, some of the pages (like a category page for example) seem to want to serve a page beginning with https.

Now if the page was a page I created I could maybe understand if it was a typo or a similar mistake – but theses are pages that are generated by the theme/site code. Its really bad because if someone opens these pages then they get that privacy/security error that google throws up.

The only other thing to add is i’m using MAxCDN and WP super cache.

If anyone could help me with this issue i’d be really grateful. Let me know if you need more information.