Help! Early pumping?


So I had a home visit the other week (I'm 36 weeks and 4 days today) the lady told me I could start practicing with my breast pump now and freeze anything I manage to get, so I gave it a go and got an ounce out between both breasts, but I've just looked online and it says you shouldn't do it before baby's born!, I'm so scared now incase I've done it wrong, the midwife told me I could but everyone online says no?