Baby’s Poo

My bby (going 4mths) is on BM through out but he hasnt been pooing everyday and i realised that only formula milk makes him poo so i swap 1 feed of BM out for formula per day. Not sure isit because of my diet that affect BM? that he dont poo everyday, sometimes 5-6 days poo 1 time and the colour and consistency is as per photo… isit normal? And i love to drink bubble tea (without pearl), will it affect my BM? like too sweet or smtg and make bby unhealthy?