My pregnant dog won't eat after vet visit. What should I do now?

You are definitely stuck in a pretty difficult situation here. Obviously as a pregnant bitch, Jenny really needs to continue to eat in order to be healthy enough to carry her pregnancy. If she is ill, she might require medications to make her feel better. The main problem with this is that there are very, very few medications that are considered safe and effective for pregnant and nursing animals. There is only one oral antibiotic in America that is readily administered to pregnant dogs, and it is called Clavamox. It is a penicillin based antibiotic. My assumption is that your vet likely gave a penicillin based injection. If this has not helped at all, she should probably be reassessed, placed on some fluids, and have her fetuses' viability checked with ultrasound. An ultrasound should be able to detect fetal heart beat, so if they appear weak or not present at all than this could be an indicator of an infectious process causing abortion. If your current vet does not have an ultrasound, you may want to go to a clinic that has this modality to give your dog the best treatment possible. Hope this helps!