My small dog has always itched all over, and does not have fleas. Now he has had episodes where he tucks his tail and starts panting, drooling, and his back legs start to cramp too, where he can't stand. This lasts for about 5 min then he's ok. What is this?

Not sure about the latter part of your question so you may need your Vet to check him out but the itching sounds like dry skin so try adding some cooking oil to his/her food  but not too much as this tends to make an animal fat if given in large amounts so use sparingly. Good luck