Periods and breast checks

Hi, I have a couple of things on my mind, I wonder if anyone can help?  Before my diagnosis in Nov last year I was on the mini pill and not having periods.  I stopped taking them immediately and am now on tamoxifen but my periods have not returned.  A blood test shows I am premenopausal.  Just wondering if they will return?  And what is normal?  Also my lump was found from my very first mammogram at 47.  There was no apparent lump, even the nurse couldn’t feel it, it only showed up on the mammogram.  My BC is lobular stage 2 which as I understand it doesn’t present as a lump more a flat hard mass.  What I am worried about is if it does comes back how is best to examine myself given the fact that I couldn’t feel it this time.  So any help with self examination would be appreciated especially from those who have experienced lobular BC too.  Thank you in advance xxxx

I was wondering if your periods stop when taking tamoxifen too xx