Our Cat Is A Male, Almost Two Years Old And

Our cat is a male, almost two years old and is normal in every way except cannot walk very well. He was found alone in a field, was about 3 weeks old and only weighed 10oz. As he grew we noticed his balance was very unsteady and his front legs kind of stomps as he walks. Mobility for his neck and head seem very limited. Hind legs seem very sensitive, he doesn't like us to even touch them. We love him so much and don't want him to suffer and would love to find something to help him. We are giving him a few pellets of arnica and hypericum once a month which seems to help, a little. Any suggestions?