Is my great dane acting jealous......

I have two dogs a Great dane (male)  and a Jack russell (bitch)  They are rather close 

The JR is on heat at the moment  and was  seen to by a male a few days ago.    At night times they sleep in a crate with the door open ... anyways the night she was mated with   a male  The great dane  wouldnt go near her and totally ignored her  and   acted as if he was seriously ill......  panting and  slumped to the ground as if he was hurting yelping when  we touched anywhere.  We even considered getting the vet out 

Anyways he took him self to bed and slept on my duvet ! next day they were fine and he was fine
Yesterday we left him at home whilst I went to feed my horses  and he  chewed my daughters doll - literelly shred it to bits!  
anyhow today we left him in the living room and hes totally eaten my sofa!!!!!!   ironically we were sorting out contents insurance at the bank!!!!     my sofa is a wreck    but is he doing it through jelousy of the jack russell ....  

he used to be a chewer as a pup but  I thought grew out of it  hes 4  now .....   

Sounds more like love sick and frustrated than jealous.  I am assuming he is castrated, but actually having an in season bitch around will still stimulate him, and castrated males have been known to mate bitches with enough provocation :D

> castrated males have been known to mate bitches with enough provocation

And the potential for damage when a randy Dane mates a little JR is astronomoical! Keep them separated at all times, for her safety.

hes not left alone with her now :)    I dont trust him at the mo . although hes usually really well behaved - saying that weve never  had her with another dog either.  Yes hes castrated ...   hes with her only when some one is there  to 'supervise'