Breastfeeding mommas- question

Hi. I'm a FTM and feel kind of silly asking these questions but genuinely don't know 😔 my baby is 6 wks old and I primarily breastfeed, and only bottle feed 2 x a day. I don't pump as I don't have much supply but enough to fill her up. I've noticed more leakage and would really like to start pumping even if its just to get an ounce or two (don't want that milk going to waste) If I pump, how long is the breastmilk good for to be out? And how long is it good for if in the fridge or if frozen? Not really sure where to start. I've been reading some mommas catch the leakage while breastfeeding the other side. Thanks so much in advance 💕