i think my terrier is having seizures(need help with info)

by tara
(PA)

My jack russel terrier named Ody feel off of the couch while trying to jump up onto it, when he fell he hit his head off of the coffee table, and instantly starting crying loudly. He also wouldnt straighten his neck out, his neck was turned to the left and I could feel that his muscles were very tense. His ears also havent stopped twitching here and there, sometimes they will twitch consistently without even being able to count a full 10 seconds in between each twitch. We took him to the closest/best animal hospital we can afford and they did x-rays on his head&neck, and did blood work also. Of course, they said he was fine and nothing was wrong. Sometimes he will be normal and will jump up and down off the couch just fine without showing any signs of pain.. but then at random times he will start crying real loud and his neck tenses up, turns to the left and he just seems very confused when this happens, also crys. We thought something might have been wrong with his leg, but i dont think thats it. If anyone has had any of this happen to their jack russel, I'd highly appreciate anyones opinion or knowledge.