Stressed out mom here needing some reassurance

Lauren

So my son is 3 weeks old and so far we are exclusively breast feeding but He’s not gaining what he should be according to last week and I had my latch checked again and it stil good but he will breast feed for almost two hours straight and he is acting like he’s starving still. I keep him awake and switch breast and everything. When I pump it’s down to like 1.5 ounces now not 3 like it use to be. I’m also just not able to get anything out for dad to feed him when I need to rest which I don’t care that much about it more the weight thing. I still want him to be 90% breast feeding really just a bottle when I need to rest or something for him to have formula. Anyone have experience with this?