I have had her checked out by the vet before i mated her
I think you may have missed the point of the health checks.
A vet check is unfortunately not what everyone was refering to.
They mean tested for genetic hereditary problems that often do occur in the boxer breed. Without testing for these problems you don't know what you will be passing on to her babies.
Also, knowledge of the bitches pedigree is essential for the same purpose. If you know little of her background, you will not know what genetic defects you could pass on to her young. These defects may not even be evident in your girl (she may carry the trait recessively) but may very well be passed on to her offspring.
Instead of breeding your girl why didn't you go back to your original breeder and see if you could get a puppy again from her lines?
Doen't this breeder you are now consulting with have any opinion on health testing in their dogs? They don't seem to be concerned with the health testing of yours.
The problem on this board is people take the issue to heart. Many new posters to this board (not refering to you) show up and take breeding very lightly like anyone could succeed in whelping a quality litter of puppies. And while may people do breed unknowingly and show success, you have the chance to be educated by people who love these dogs as much as you do.
I hope some of this reaches you in a positive manner, I don't want to anger anyone. I just want to tell it the way it is, some people chose not to hear. I wish you luck with your girl, I hope everything goes smoothly for her.
To help answer your question....
Feeding pregnant female