What do these symptoms sound like in my dog? Vet said it's nothing but she seems in pain...?

You can get another opinion. I have to get my Misty's glands cleaned out every so often. But she scoots on her back end a lot after she has it done. Like our vet says her itches and that is the only way she can itch it. As for her eating gr and then vomiting they eat gr because their tummy is upset and that is why she vomits after she eats it. Good luck