Is this unusual for your child? My daughter only poos once every 24-36 hours and has done this since one week old.. (now 6 weeks). It does cause some wind issues in the few hours before she finally poos but what comes out is normal & usually massive! I tend to find she strains on and off a few hours before actually getting it out!
It sounds normal, sometimes they can go a few days and then full on explosions. Try doing gentle pressure on the lower stomach from right to left, or moving his legs like he's cycling as that can help get things moving.
My formula fed baby hasn't had a poo since yesterday and yesterday he had a few explosions . Today nothing ? He seems like he keeps trying to poo how long before he qualifies for being constipated ?? Is this somthing to worry about fyi first time mum