help with pooping please😩

Hiya,
just looking for some advice with my little man he was born prem at 34 weeks on the 9th June. We've been home a week tomorrow now. He is pooping like mad i'm not sure if it's normal.

He is currently on 3 hour feeds having around 40-80mls and fortifier with 2 of of those feeds for his weight gain. He lost 5% of his birth weight but since we've been home he is now above his birth weight. I'm struggling to bring his wind up but he just passed stinky gas a lot and is constantly pooping. His bum started to get sore in the nicu so we've been on it with changing him. But in the last 2 hours he has gone 3 times. It's yellow and was seedy but now it's getting runnier or and goes into the nappy a lot of the time if that makes sense it's not very seedy. He's only on breast milk.

Is this normal? my eldest son had a milk allergy and his constant pooping if reminding me of that but he doesn't display any of other symptoms to an allergy. He's a very relaxed happy baby very alert doesn't scream unless it's coming up to food time no rashes except his bum