Sleeping Pattern

Hi mommies. Anyone here who encounter na baliktad ang body clock ng baby? My baby sleeps soundly at morning. Usually 10 or 12 ng tanghali tulog sya ng mahimbing. As in kahit anong ingay hindi sya nagigising. He will sleep 10am to 8pm straight. Then sa gabi naps lang ang ginagawa nya. I dont know how to fix my baby's sleeping pattern. Naaawa naman akong gisingin sya sa morning dahil yun lang yung time na mahaba ang tulog nya. Almost 1month na syang ganto. 😞 By the way, my baby is 4 months old. I dont know kung part ba to ng sleeping regression or what. Any advice po? Thank you