Is this abused behavior or muscle spasms?

[Kurra]

I am having a problem with my dog. We rescue him from the road in May. He was really active, loved to play fetch. We called the number on the Tag and it was a dead in. We kept him. After a few weeks with him we felt that he had been beaten. He has bitten some people while protecting the house. In July or about that, he started to excessively licking the air. I had read about the excessively licking and today on this site. since I started back to school, he has started to pull away from me and stop playing fetch. he is not that active, We don't know how old he is but from the number we found that vet office said he was seeing in 2007. So he is over 4 years old. Last week he started to whine out. It look like he was having a muscle spasms. He has had them a few times. He has come for support from me and other times he will go under the couch. It seems like when he is scared or thinking we are going to hit him ( when we are not) that he acts like that. I have went to touch him and he seems to pull away and act like we will hit him. he will be hunching his back. However, when he wants support I can touch him everywhere and no where seems to be in pain. After the spasms when he is normal I can touch him anywhere and he is fine. Is this a sign of stress, or an abused dog?