How do I remove thumbnails from a post?

Hi, my blog is philandersonphotography.wordpress.com

I just started on my blog but one thing is really really frustraiting me. Whenever I post a blog update and include images in the post, the images will appear at the top of the post in thumbnail form aswel as a bigger image in the post where i originally inserted it. So basically, If im making a post and half way into the post I insert an image, that image is included half way into the post as I wanted, but its also included right at the top of the post as a thumbnail. How do I remove these thumbnails from showing every image i ever include in a post? I cant work out how to change this. I have the paid upgrade to edit CSS. Or is this something to do with the theme I’m using?

Is someone able to take a look and point me in the right direction with this?

I managed to get around the problem by not inserting images into a post mid-way through, I just add an image to the top of the post, and changed my thumbnails to be large, so the images on my blog are infact just large thumbnails. It just means now I cant ever insert an image half way into a post.

Hopefully I’ve explained this well!

Thanks.