Water for 5 week old

Yellow and green poo in breastfeed babies is completely normal.. I wouldn’t say he is dehydrated if his urine output hasn’t changed.

Straining is also completely normal as baby is just learning how to use their bodies.

If it’s frothy or accompanied by other symptoms such as poor weight gain, rash, runny nose, then could be down to other issues. But if it’s just green and baby is happy and content it’s probably not anything to worry about.

I personally would try and speak to a midwife rather than GP, or visit a local breastfeeding clinic for advice if you are still worried.

https://llli.org/news/babys-poop/

I'd speak with a health visitor

Some GP’s are very outdated, and they’re really not that clued up in every single area of medicine, especially where babies are concerned. This is awful advice. It’s the kind of advice that would be valid for a constipated formula fed baby, not for a breastfed baby with “suspected dehydration” - he doesn’t sound dehydrated at all. His poops sound normal, and the straining is also very normal for all babies, because the experience of a bowel movement is so new to them they often strain and grunt in discomfort as they’re getting used to being outside of the womb. A health visitor might have better insight but honestly your baby sounds fine

My baby pooed after every breastfeed as a newborn! She also had green poos when she was getting too much foremilk, make sure one boob is completely emptied before you offer another.

You should never give water to a breastfed baby, both of my babies have poo’d tonnes of times a day no issues x