tips please?? good milk supplie but cant pump??

hi moms, i need some advice. my baby is EBF and i have enough milk. but i would like to pump and breastfeed and put the pumped milk in a bag in the freezer. BUT i have an issue with pump. i dont why.. it just dont work! i tried pump in style by medela and then the avent electric double one. i get sometimes 2 oz, 3 when i am lucky. morning i can get 4 oz.. so i pump for 15 min, after maybe 10 min nothing come out, my nipple starts to hurt but when i press on my boob, the milk come out in any directions 😂 why cant i pump?? when i know i have milk.. i already put some hot when pumping, it seems to help a bit but idk. i also try to be relaxed when doing it and think about my baby! nothing seems to work.. help 😭