So sorry that you have been diagnosed with BC at such a young age. I was diagnosed at 47 and experienced a very similar thing with my periods during the first 3 rounds of FEC chemo. I kept informing my onc but she was not overly concerned but a bit surprised that chemo did not stop them sooner.
I finally had 2 lots of bleeding very close together just before my 4th chemo which was a different chemo drug, Docetaxel (similar to taxol). That was then the end of it for me and I was in chemo induced menopause. Being 47 at the time, it is most likely that I will stay in menopause but it can be different for younger women.
I think it is always a good idea to check out anything that you are worried about with your oncologist as this process is hard enough without worrying about something that might be ok.
Hope that your doctor can talk your concerns over with you soon. Take care. Deanne xxx