Feeding vs. Pooping amounts

My LO is 2 weeks and a half weeks old. Today he woke every hour for 100ml of milk (he is bottle fed breast milk or formula as he doesnt like the boob for some reason). He is constantly straining like he is trying to push out a poop but hes only doing a tiny poop once a day. Im worried Im doing something wrong and have upset his tummy. Any suggestions?