Tumor swelling/pain during neoadjuvant chemo? Worried.

Hello all. This is my first post. My BC is stage IIb, but I was hoping more of you in the stage III group had experience with neoadjuvant chemo than people with less advanced staging seem to have.

I have completed AC and am getting my 10th of 12 weekly taxol + carboplatin treatments tomorrow. I have not had much shrinkage of my tumor cluster during chemo, but my doctor assures me that my tumor could just be dying/dead with scar tissue left behind. I guess many women don't experience dramatic shrinkage with chemo. I had minimal shrinkage with AC, but on taxol and carbo the tumor seemed to become a little flaccid and "lumpy", indicating that it was being eaten away like swiss cheese. So says my doctor, anyways.

Then, two days before my treatment last week, my tumor started to swell in size and started to hurt a lot. It has always been slightly painful, but this is worse than it was after the biopsy. The skin became hot to the touch, and became a faint reddish brown over the tumor site only. The pain got worse over about 2 days and is now consistently radiating into my armpit (I do have 3 lymph nodes involved, but they have not been palpable for quite some time). The pain is probably a 5 or 6 out of 10, and feels like my breast could pop like a zit. I still received my treatment last week, but was started on prophylactic Keflex for 10 days and sent for an ultrasound. Ultrasound showed no signs of infection (abscess, mastitis, or cellulitis), and that was all they told me.

This is day 7 on antibiotics, and I have no change in symptoms. I have had no fevers or chills. I am convinced this is not an infection. But the pain is bad and the swelling is significant, and I'm very concerned.

Does anyone know if this is normal? Is it possible that it is just inflammation as my tumor dies from the chemo? I'd like to believe so, but it seems kind of sudden. The skin discoloration over the tumor is also disconcerting. Is it possible that my tumor is growing or is not responding to the chemo? How would I know?I see my doctor again tomorrow before treatment, so I am definitely asking her about this. However, I was hoping maybe some of you had experienced a similar situation and could give me a little insight.

Thanks in advance :-)