sleeping ALOT more than usual

my son was one month premature

hes been developing really well, and hitting his regular milestones.

the past few days he has been sleeping so muchj and im not sure why. I know there should be a growth spurt around 3 months but my son is 4 months...
his normal sleep schedule is sleep from 8pm-700am only wakes up once to eat around 4 am
then naps at 12am-3pm

now he is sleeping from 5pm-630 and not even waking up to eat. i have to feed him while hes still sleeping.
then 8 am-11 am. then 12-3pm and repeat.

i might be over concerned but not sure if this is normal or not since hes my first.

i think your freaking yourself out, if the baby is tired it'll sleep. there isnt any set growth spurt chart, they happen at any time.

sleeping until 630 am *