Pumping before milk comes in?

My baby is only 2 days old but is having a hard time latching. It is a hit and miss. Sometimes he latches and will feed for 20-30 minutes and other times it’s 5 minutes and he won’t latch any longer than that. The hospital suggested I supplement with formula in the meantime. My milk is not in but I am able to express lots of colostrum. Wondering if I should pump during the times he doesn’t latch or feed for long? Is it okay to pump before your milk is in? I have an appointment with a breastfeeding clinic on Monday but in the meantime I feel so lost! I’m new to this and would appreciate any advice from other Moms! Thank you in advance!