Breastmilk question?

So I am a ftm and my son is 6weeks. I have milk supply problems as I cannot eat enough calories to sustain production due to a medical procedure I had done so I am supplementing. My question is this: I pump multiple times a day and I am finding that I can barely get an ounce out of my boobs via the pump but when my son sucks or I squeeze my nipple, milk sprays everywhere. I don’t know if the pump is now working or what? I have a Lansinoh smart pump. I used to be able to get 3oz, but now barely a sip comes out into the bag. I don’t understand why it wouldn’t come out when I pump but when I hand express it does 😔😢