Why can't I post images? Image URL invalid using multiple hosting sites

Hi,

For some reason, when I put images into my post, when I try to actually post it, it says image URL invalid.

I've tried imgsafe, postimage, plus a few more that you guys have suggested. But it keeps doing the same thing! I'm putting it down to steemit, what do you think it is?

Please help, it's so annoying. They show up in the editor, but then when I try to post a wavy logo appears on each image.

Thanks in advance