Girls, hello ? Maybe someone had this too? Son is 1 month old, we're b…

Girls, hello ? Maybe someone had this too? Son is 1 month old, we're breastfeeding, in the first month we gained 1.300, tell me when we feed him, he eats, within seconds-two, he spits everything back out, he spits it out well, and the milk is straight, it started a few days ago, before that he also spitted it out, but not as much, tell me, maybe someone had this too, what could it be?