Sorry to hear Jasper is distressed... this must be upsetting for you :(
The root cause of him pulling at his fur doesn't seem to have been discovered?
(or addressed with specifically targeted treatment in that case)
Licking/picking at an area can be kitty's effort to ''lick away'' pain or discomfort.
Has he had softer than usual stools recently (not meaning smelly or poorly - just not hard) and has he ever had his anal glands checked and/or drained?
Have you observed any twitching or rolling in the fur along his back?
Have you considered anything environmental that he could be allergic to? ... it would be a product introduced to your home more recently and not long before his symptoms began.
For stress relief you could ask your vet about Zylkene... when you have some professional advice about this medicine you can get it prescribed (tablets I think) or you can buy it infused into a dry food
http://www.zooplus.co.uk/shop/cats/dry_ ... iet/356888