Kim
I really hate to hear your discouragement. Here is a very good guideline to follow when fostering. I know how frustrating an illness can be since we own 17 cats. You probably read about our flea fiasco we just recently went through. We had to medicate ALL cats, bomb the house, keep the cats away from the pesticide etc. It's not easy when things go wrong, but your efforts are well worth the aggravation. Please don't give up yet! Here's a little first fostering advice. I hope it helps:

It is strongly advised to only foster one litter of kittens at a time. You will soon find that one litter will demand a great deal of your time and it is important to care for litters properly and not be overwhelmed with the responsibility of two litters. If you do foster two litters of kittens, it is of utmost importance that they are kept in separate rooms with absolutely no contact between the two litters. One litter may become ill and placing two litters together will expose all kittens to illness and disease. It is extremely important for you to follow a quarantine guideline. Kittens should be kept in a confined or quarantined room for at least three weeks. Even after the three-week quarantine time, it is still advised to keep both litters separate, even until the time of their departure for surgery. Always wash your hands thoroughly after caring for all foster kittens, whether you are caring for one litter or two this will help minimize any health problems. Fostering is demanding work and it is wise to start out slowly and as time goes by you will begin to know your limits. This quarantine also applies to your pets at home. It is VERY important to seclude them until all questions of illness has past.