Hi,
Was going to suggest a vet visit but if your vet found nothing wrong last week it is unlikely to find anything now. Could something have spooked him lately, like a cat or a weasel or even if there had been large birds flying overhead. He certainly sounds like he's nervous. Is he behaving normally when not being handled? Has anything happened while you have been handling him such as a loud noise or other unpleasent event? Might be a case of rebuilding his trust with lots of treats when you handle him and making him feel secure again. Is quite sad for you when you've had him so long and he's been so handlable. Lets hope its just a blip!