My bitch is 4 and a half weeks pregnant. She has gone off her food. Today only eaten an little bit. we have had pregnant dogs before but none have gone off their food. Is this normal??

Very common

So i have no need to worry then??

No need to worry. As Barbara has said it is very common. It's like morning sickness in a way. The bitch feels a bit off colour, just like a pregnant woman can. It doesn't usually last long, just a few days. :-)

is there any thing i can do to make her feel better. i feel so guilty
She has got more clingy. Always wanting my attention and claws me when i stop stroking her

Clingy is perfectly normal too.  Mine need reassurance and closeness when pregnant.  In fact, it's often the idicator that the mating was successful!  Going off food is normal, although I've had bitches go off it for so long, I've wondered however the pups can get any nutrition, but it has never produced weedy pups.

you are doing all you can for her :) lots of love and cuddles ...and if you think shes clingy now just wait till shes about 7/8weeks lol you not beable to peel her off you :) good luck x