Ay, one week is quite long talaga, I'd suggest checking with your baby's pedia asap kasi they can see if baby is uncomfortable or if there's something blocking, especially since mix feeding sometimes needs a bit of adjustment. A few of us mums went through this din, and honestly the gas without pooping can mean the baby needs a different formula or feeding adjustment, so better to get professional advice para ma-ease your mind and baby's belly right away.