Did your bra size ever change?

I've always had my cup size in mind.. having to come to terms with excepting my body and being a proud member of the itty bitty titty comity. I've always wondered if I was going to change.. worried that i wasnt women enough. Recently I went to go get measured for the first time ever ( I know it's bad) never really knowing my actual cup size. I knew I was wearing the wrong size bra because i never bought them myself (mostly wore hand me downs from my sisters) 😂 but I always thought I new what my size was even if I never wore it. But apparently I went up a cup size! Is this foreal? Or is it temporary? I was measured around the time I was about to get my period so I was wondering if that was the reason..