Almost 3 year old is holding pee for too long?

Molls

My toddler is potty training… doing well.. but holding pee for anywhere from 2-6 hours!! Is this normal and ok? He also hasn’t pooped since yesterday morning :( I’m worried he will make himself ill… we’ve tried potty training a few times and it always results in this. Me being worried and then giving in and putting him in a diaper again. Advice much appreciated!!!!!!