I'm not a doctor, or a lactation consultant (yet), so take this with a grain of salt.
First thing I'd do is go back to the doc and tell them your symptoms. Explain that the pain never cleared up.
It is normal for some women to experience pain like yours while breastfeeding. Well, maybe not normal, but you're definitely not the first person I've heard talk about pain like that. It can come after the breast is emptied.
It's fine to nurse the baby when you're on antibiotics. I did it with both my girls and they never had any type of side effects from it. Breast milk is best, even if it has antibiotics in it. I can't swear to it, but I dont' think much of the antibiotic gets into the milk anyway. Not to mention, you're going to be fighting engorgement and that can lead to pain. I would imagine that you're pumping, but no breast pump is as effective as a nursing baby. Personally, I'd go back to nursing her on a regular basis, unless the doctor's have advised against it because of the infection. (Which I don't think they would do, but again, I'm not an expert.)
Most of the times doctor's will tell you if the symptoms are no better by the end of the course of treatment to call back. However, my experience is it usually takes about a week to see some type of relief.