Show steer won't calm down.

I bought a steer for 4-H in November. He is a Hereford angus cross. Last weekend we took him to the fairgrounds for weigh in and he freaked out. When I'm working with him at home he pulls his head but he never gets away or kicks, but at weigh in he pulled me down to the ground and rammed someone into a fence and kicked me. He is also not gaining weight. He is over a year old now and only weighs 720 lbs. my 4H sponsor told me that nervous calves like him never really gain weight or are Showable. Is this true? Or does anyone have any suggestions about what I can do to help him?