Ken Jennings’ confidence after being named full-time host of Jeopardy! has gone “straight to his head,” according to a sensational report which said his ego is ruffling feathers on-set. Insiders said that “his britches are bigger than ever, and they were pretty big before,” RadarOnline.comhas learned. “He complains when his suits don’t fit, even when he’s up and down on the scale,” alleged tipsters who claim that his antics have been causing quite a stir. “He wants more makeup, then says it’s too much. He gets mad when people don’t laugh at his jokes. He carries a grudge.” His co-workers were …