How do I handle my 6 weeks old baby who is always crying and needs to be held and walk while holding him. knowing that they are twins and I can't keep holding him since I have his brother to take care of him too. N.B.: This baby was born underweight (1380 g) and was kept in the NICU for about 18 days.
Can you wear him? My preemie LOVED being worn, and it freed up my hands to do the other things that needed doing. Try a Moby wrap or something similar; there are oodles of how-to videos online that show you how to properly tie is so he's safe and secure and able to breathe freely, and you get your hands back.
Even I have twins 11 mo old and one of them is somewhat underweight, tiny and very Fussy. She loves crying and constantly pokes and loves troubling her Twin sister. So I let her CRY. It helps in removing pent up frustration and makes her Feel better. I wait for 15 minutes to let her stop crying by herself and when she does stop, I pick her in my arms and give her lots of hugs and cuddles.