To see the anal glands, you usually have to lift the tail completely up,they surround the anus. Joey's would occasionally fill with fluid, and needed to be emptied when he was a puppy. Most dogs empty the glands when pooping, but for some reason, Joey didn't empty the glands, and the area around the anus would be slightly poofy, and he would start doing the butt scoot, which is a sure sign of a problem. This does look like the testicles to me, and they are located further down from the anus. You do not want to squeeze the testicles! Here's a link with more information, it is not clear in the picture what it is, but I hope it's not the anal glands because that would indicate a serious problem, and you would need to see a vet immediately.
Anal Sacs