Baby isn’t sleeping

My son is a month and for the past week or so I noticed he isn’t sleeping like he used to. Before he would sleep for 3 hours, be up for like an hour, sleep another 2-3 hours, repeat, at night be up about 2 hours before bed then overnight sleep 3-4 hours. A few times he slept almost 5 hours.

Now during the day he isn’t sleeping his regular 2-3 hours. He’s sleeping maybe 30 mins and will wake up. Then be up for 2-3 hours then sleep about 30-45mins and be up.

It’s 11:50pm, and he just went to sleep (we’ll see if he’s actually sleeps) but he’s been up since 4pm basically. Between now and 4pm, he slept the most maybe 30 min to an hour.

Anyone else having this issue ??