Breast feeding (pumping)

When did you all start pumping off milk to get a freezer supply? I was told that when or if my breast start leaking after 36 weeks I can start pumping, I just want to make sure this is accurate information (it did come from a doctor) but I know pumping (nipple stimulation) can bring on labour, that’s why you can’t do it till 36 weeks.

Did anyone else start pumping before baby was here ? And if so how was your experience.

The reason I’m asking is because with my first, I had so much milk supply in at 36 weeks, my boobs would pour milk, but I decided not to breastfeed so it went to waste.

This time I want to give breastfeeding a go, and would love to be able to start saving up milk if it’s anything like last time.

Thanks :)