My 2 year old poo isn't normal help?

So my 2year old has been really off and funny with food for the last week now, he just won't eat anything. Normally he will eat all his fruit and veg but the last week he has pushed away nearly every meal. I know some kids go through a fussy stage but his pop's have been REALLY lose and sooo smelly! Like eye watering smelly it's also made his bum red raw as if it's burning him?!

I'll attach a picture of one of his nappies if anyone has any advice or could possibly know why?

Friday he was at pre-school and I got told it was a very pale colour/greeny

He has got the doctors tomorrow, but I'm just worrying to much!