Yep, super common sa ganitong edad, a few of us mums went through the same thing, nakakaalarm talaga sa first baby! At 1 month, usually it's just because their tummies are still adjusting, or sometimes they're swallowing air while feeding or crying. Try keeping baby upright after feeds for a bit, burp in between, at don't worry too much if it's just a little spit-up, pero if it's projectile or your baby seems uncomfortable, best to check with your pedia para peace of mind.