I don't know if I'm just being a nervous first time mum or if my little guy is sick...

In the last 24hrs he has suddenly gone from only having 2 pooey nappies during the night, to a pooey nappy after every single feed. I'm FF every 3hrs at the moment. It seems like he's pooping constantly! He's also drinking a little less (10ml generally) than he was. I said to mum earlier that if he didn't finish the bottle I was about to feed him I would take him to the doctors, but he finished it and the next one - and wanted more!! - and now he hasn't finished this latest one again. He doesn't have a temp (I've checked 3 times this evening lol), so I just don't know if this is normal behaviour or not