Newborn farts smell like rotten eggs

I have a breastfed 5 week old with rotten egg farts! Is this normal?? He goes through periods where he really struggles to fart/poop by himself so we have to do bicycle legs, tummy massage etc. but today he’s been doing the most rotten farts!! We literally have been thinking we had a sewage problem all day trying to figure out where it’s coming from and just realised it’s him 😩🥴