My baby is 45 days old & daily crying at night what is the reason of crying

comfort is what it needs. keep a pattern or routine given below 30 minutes before bed time close light in your room. put on soft soothing low tone music feed your baby put on a fresh diaper. use diapers and not cloth. before putting diaper, clean and powder your baby's bum and apply diaper rash cream bundle up your baby in the cloth wrapping no swinging, rocking etc... just put him near you and keep your hand on him. let him hear your heartbeat. this was the sound it heard when in your womb. it's the most soothing sound for him. ensure the room is cool as babies feel as hot as adults do. so don't put blankets etc.on baby. keep music on till baby sleeps. if he wakes up crying at night again, take him close to you and keep hand on him. all it needs is soothing. chk for any diaper soiling. always keep baby's feed ready 5 minutes before his normal feed time and give him while asleep.