do you have any idea why he is doing this? and why he would just start doing it recently and never before? its realy frustrating

Could he be bored? Could you put one of the other horses in his paddock so he has a friend. Then perhaps they could scratch withers instead of him munching his rugs? Of course you then have to consider that they could kick each other. Try googling anti-chew equine or horse products. Let us know how you get on! Good luck.

well he has a pony in his field with him and horses either side. I thought he may be bored cuz of the snow with no grazing and not being excerecised but he started it a few weeks ago when he was being ridden everyday and there was no snow.