Why is my maltese x shitzu puppy continually trying to bite his bum and tail?

I have only had him for just over a week, he is about 2 months old. I have never owned a dog before and was just wondering, should i be worried..??Any help would be great. I have booked him into a vet but couldn't get in for a week. Thanks

Part the hair, look at his skin, can you see tiny black dots?? If you can, they are flea droppings. Treat for fleas.

Check his waste next time, it sounds as if he has a type of intestinal worm. Also check for licking and scratching of his .. bottom.Many animals can get poop caught in their fur around their bottom which may cause irritation but I highly doubt it. Another thing which may be causing it might be ticks or fleas.My first bet is worms.Get your doctor to worm him or do it yourself. With a new dog in your house it's a good idea to make sure he won't pass on germs to you. BUT- Then again, if you and your vet find nothing, don't worry, he's a little guy. he might be just chasing his tail for all we know..