To ease your fears, a doctor visit would help - trust me, they'd rather you bring him in than assume it was okay.

That said, SBS is VIOLENT - if you were jiggling him to get him awake, I doubt you shook him hard enough. SBS is when their head and neck rattles around violently. It's heartbreaking but there are video demonstrations both animated and real-life on a doll. Be prepared to tear up thinking about the little ones who suffer this!