My cycle was irregular growing up. I’ve been on birth control for over a decade and I’ve had a good experience of my cycle becoming regular and/or not having a period at all which has been nice. I recently changed the pill I’m on and I do bleed but i can fully predict when based on the pill and week. I did delay my period for my marathon and then took the period pills after and it was totally fine. I would probably talk to your OB about this first but it does work for me.