Duplicate images

> I prefer my post images to appear after the blog post title I incorporate the image in the main text box

This is a bad idea. If your theme does not support this image configuration, just update your blog post template.

https://developer.ww.wp.xz.cn/themes/functionality/featured-images-post-thumbnails/

To comment on your issue, see attached – either you have added it twice using Add Media, or your template is whack :

View post on imgur.com