My baby not pooing

My baby is 3 months plus going 4 months. She didn't poo for 6 days so we went to the PD. The PD put suppository and she poo at the clinic which looks like 1 or 2 days worth of poo only She is on biogaia probiotics already everyday. Now it is 2 days after the visit to the PD but she is still not pooing yet. We did massage her stomach not still never poo. Not sure why she can't poo on her own already. Very worrying. She is drinking formula milk & breastmilk.