She’s a golden/shep mix. She’s fixed. She doesn’t have worms. I keep catching her rubbing her butt and I’ve been finding skid marks on my carpet! Please help!

My friends dog has black colored worms coming out of its butt. I looked online to try and see what it was and i cant find anything! I want to help them but I dont know what kind of worm it is. They dont have a lot of money so wont be able to take the dog to the vet. I know that is horrible and they really should not have gotten a dog they couldnt afford but they did. does anyone have any idea what kind of worm this is? Im really courious.

My dog was prescribed heartworm medication. He took his pill three days ago, and now there are white worms coming out his butt. Also a few months ago he was given a shot for a different type of worm. Are they coming out because of the medication? Is this normal?

i give him the full worm treatments on the first day of every month according to his weight and he’s still scratching. i have heard of anal glands, what are they? could they have something to do with it?