Hello mimi, look I think the easiest way to preserve your fertility is to use Zoladex while having chemo, particularly if you dont have time for preserving eggs, etc!....it is still experimental but at the moment it is showing 98% of efficacy! And as Joy K explained once you stop taking it, the effects are reversed quite rapidly. Talk to your doctors about it! I used it and the menopausal effects are reversing quickly!!
Your fertility most probably will not be affected as you are young, but it also depends the amount of drugs and cycles, type of drug (i.e. Cyclophosimide affect it the most), what I did is check medical papers to get my own opinion about everything, a good place to look at is "pubmed" and then you follow the indications, e.g you can type fertility and breast cancer and it will show the latest scientific info about it! For what I have read if your nodes were negative you are in a better position!! yeay!
All the best and please take time to think about important decisions before doing anything, that is my little advice, listen to your heart and body darlying!! And be strong!!