My 7 months old will sleep 9pm wake up at 1 then every half hour after that till 5am why ?he will wake up screaming

First have his ped-: iatrician check that he's healthy. At a consistent bedtime, read, soothe, brush his teeth, then put him to bed drowsy but awake, without bottle or pacifier, to learn to self-calm for sleep. If you ignore his night-crying, it will 1st increase, then stop. The AAP's HealthyChildren.org's tips on graded ignoring, going into his room without making eye contact or picking him up, may suit you better.