Congrats to your pregnancy! As others have replied, it's normal to have a few drops of colostrum at this stage especially if you do the pumping. If you will like to collect the colostrum to store as spare, I will suggest you to try hand expression instead which usually yield so much more.
you're producing colostrum right now which you can choose to collect and store it after 37 weeks onwards. your milk will come in after your baby is born and it's also up to you if you wish to tandem feed your both child.
It’s normal cause your milk is turning into colostrum to prepare for your newborn’s arrival. You can start pumping or latching again when baby is out 😊.