Hope, Zyon's poo has always been fairly green, but not frothy, just green!? When he was on the formula feeds (regrettably) his poo went Yellow, but the MW said any formula lactose free or not would change his poo!
He has never had blood or mucous though!? Sorry I cant help, I'd maybe trial the gaviscon as you can buy it at chemist (Infants Gaviscon) & see how he goes, I am REALLY annoyed I was told to put him on formula, as he is heaps calmer/happier with the gaviscon, but didnt change on the lactose free formula, if anything I'd try to lactaid/lacteze drops on my nipples & feeding that with the gaviscon to prevent giving up the breast!
I'd also get MORE OPINIONS!!! As I found out many cant be bothered & just wanna fob you off!!!

Good Luck!