Bottle feeding question

rosalind • Wesley John 3/14/20

So my son was exclusively nursed for the first 3 weeks. The dr told us that this was a good time to introduce a bottle to get him used to taking one for when I go back to work and my fiance also felt like he was having trouble bonding with our son, so we figured it was a good idea. I was afraid that he would end up having nipple confusion, but he has been able to switch between breast and his nightly bottle (of pumped breastmilk) perfectly fine. But the past couple nights or so, he nurses for 20 minutes, but then gets fussy and screams his head off. My fiance then gives him 3oz in a bottle and then hes content. Hes fine nursing the rest of the day and night, it's just at that one time. I feel like nursing for 20 minutes to immediately drink 3oz out of a bottle is a lot all at one time. He does spit up quite a bit after, too, but he wont settle down for anything other than a bottle. Hes 5 weeks old now, btw. Has anyone else had an experience like this?