Your pictures are probably to big to upload, so in all probability every time you try to upload it says "Upload Failed". I downloaded this program called Picasa and it enables you to shrink your photos, you should do the same. Just google Picasa, it even has a help menu that tells you how to shrink a photo. I hope this helps.
using picassa you can also host pictures, you can choose the size and it will give you a custom embed tag. than copy and paste that into the "insert image" space on the post.
edit: you will need to use an existing google account to login, or create one for free.
if you have a gmail account you already have a google account. If not its easy to create one for free. Using picasa you can set up an online album for photos. Simply upload them as is. when you click on a photo to view it to the right there is a link which says "link to this photo" Click it. There will now be a link which says "link" and a link which says "embed image" Below that if you put a checkmark on the "image only(no link) option. You can than select the size. Either a thumbnail, small, medium , or original size. This is a great way to easily host all of your images in folders for free, without taking up space on your computer. Once you select the size simply copy the "embed link" which they give you. Than click "insert image" in the post you wish to put the picture in. Paste the link, you will now have a picture embedded in your post at whichever size youd like without altering your original image.