You say she's still eating but not much....this concerns me
I hope you've already educated yourself about the extra dietary needs of a pregnant bitch and what she will also need to consume while she is lactating.
(Protien, fat, suppliments)
How old is she now? Is she is good health?
Do you know the male dog in question? (and his medical history)
Are you aware of the signs and treatment of pyometra?
This can be a very serious and life-threatening condition that needs immediate Veterinary assistance. http://www.angelfire.com/biz4/MastiffBreeder/pyo.html
Have you decided to wait until after she "delivers" to seek the help of a professional? Are you planning on having an ultrasound done then?
Have you had experience with any other type of animal husbandry or had any formal training in the birthing process?
Have you familiarized yourself with the proceedure, equipment and supplies you will need to do the feedings yourself, (about every 2 hrs) should the bitch reject her puppies? (not uncommon for a 1st time mother or one who is young or ill from infection)
Are you well versed on the various conditions and diseases that the pups can end up with and have a Vet in waiting to assist you in treating them?
Do you have an idea of the vaccination schedule for the pups?
Are you familiar with Parvo and how crutial it is to avoid it at all costs?
I understand that this is probabaly not a picnic for you and that you most likely did not put your pet's heath at risk, intentionally. I'm also not doubting your love for your companion, I just want you to be aware of the "what if's" and the "what nows" that will possibly arise with something like this.
It can be very costly to say the least but most of all it can be very heartbreaking for you, in the end, especially if something should go wrong and you were not prepared.
Please let us know what you decide to do and how your girl is doing.
Most times when people make a post like yours, they feel somewhat ridiculed by the (well meant) responses and subsiquently don't return to post an update/outcome, which can be upsetting to those who are genuinly concerned and hoping for the best.
If you haven't already, please see a vet, if for nothing else just to put your mind at ease and then take a deep breath and do all you can to ensure these little ones are protected and taken care of, which I'm sure is your main concern.
What has happened is done, all anyone can expect of you now is to learn from it and move forward with the pup/mom's best interest at heart.