Bucking Out Of Fear Or ness?

I recently got a 16hh bay horse and he seemed really quiet and sweet. The man which i got him of forgot to bring a girth along with my new tack when he arrives sunday night so it was tuesday before i got one. myself and my dad went down to get him on the tuesday and considering he was so quiet i decided to bare back him as my dad was leading him. i leaned on him first then got on but as my dad went to lead him away he began bucking and bunny hopping on the road, he tossed my dad down onto the ground and i managed to scramble of without getting thrown off, as im doing important exams at the min i cant ride him for fear of falling off. im wary of him now. i tacked him up last night to get him used to the tack but he seemed to be spookyesh. I desperatley need help here !!!