Images Are Not Aligning In Post as they Show In Edit

So I’ve spent ALL DAY trying to find how to place images side by side in WP. (It’s definitely seems a lot harder than in Blogger!) But I finally thought I had it–I had 5 images placed (using add media and then making the images about 100 x 100, and dragging them where I wanted them). When I’m editing the post, in visual mode, I see that the images are as they should be–lined up side by side and looking nice.

BUT–when I click “preview’ or post it privately, the images are HUGE and they are not side by side. THey go up and down. How can I fix this? Is there code somewhere that I can use to do this without using add media?

I’m stuck here, and have no idea what else to do. And I don’t want to publish the thing cause it looks absolutely horrid as it is. Why is Edit Mode showing me something completly different than preview? Is 100 x 100 too big? (Note–I did try to go smaller and it still in preview each image is too large and vertical, instead of next to each other.) Any help would be much appreciated. I’m tearing my hair out, here!