Has anybody who's bitch has had a litter ever noticed a fishy smell which I think is coming from their bum?

Anal glands???

Sorry yep its coming from her anal glands..

Is this normal or should I be really worried?????

She probably expressed them with all that pushing!! :D
Have you given her a really good wash around the back end?  Especially any trousers as that foul smelling stuff can really travel!  After shampooing, use a tomato ketchup rinse (and then rinse that out) to remove the smell. 
If she is still making the nasty smell, then she really needs the glands to be emptied.  That's a Vet's job if you don't know what you are doing.  If left when they are full, anal glands can become infected and/or impacted, and that will be a reason for concern.

Thankyou Val!!!

I have written my first post all wrong as she has not yet actually had her pups, If she is pregnant she will be 3 weeks tomorrow.

I was worried about Pyometra as she is slighhtly showing little bits of discharge.

I have called the vets but cannot get an appointment unstil Friday

Jay

I reckon ours get a fishy-type smell when they're ovulating or have just been served.   It's not particularly unpleasant (can think of worse!!!).

I know that's not the case now - just added it as a point of interest.

Jo and the Casblaidd Flatcoats

Jay, you may find that giving her a dry weetabix every morning will help.

Thanks I will try this tomorrow

Jay

what exactly is a tomatoketchup rinse?

Tomato ketchup diluted with water.  It removes any stubborn smells - anal glands, fox etc.

Sometimes when two dogs are tied you can see a very slight discharge coming from the bitch's anal gland and an awful pong, the dog swelling and pulling when they are back to back is emptying the gland from the inside (if you see what I mean).

One of my girls had this smell around 2 weeks after mating, my vet did put her on a course of anti-biotics, just as a precaution incase she had a slight infection after the mating.

But she's fine now, blooming well and no smells..........lol.