I didn't try expressing until after birth when I was unexpectedly separated from DS2.
Honestly it is THE MOST frustrating, demoralising experience so try not to set too much store by it!
Colostrum is supposed to be produced in tiny amounts, this is absolutely normal - between 1ml - 5ml at a time.
It's completely normal to be able to express only a fraction of what you're actually able to produce. This is because expression is not nearly as efficient as a baby at removing milk.
Modern pumps are also not very good for colostrum removal because of the closed filter system - an exercise in frustration management when I managed to get 0.002ml and it was all stuck in the sodding pump mechanism and would harden and solidify before I could get to it and hoover it up with the syringe!
Then by chance I managed to hire an ancient pump from a pharmacy (that was its own challenge) but because it had no closed filter system it allowed the colostrum to drip straight into the bottle - result!! I was OTOH paranoid that this old pump wasn't BPA free or properly sterile so I was a bit anxious about using it.
Anyway - would it have made a huge difference to have loads more colostrum ready to go? Probably not. He got a bit of formula when he was born. It was not the end of the world. We are still BFing at 2yo :)
I have heard this is being advised across the board now and I think it does have some benefits, but I also wouldn't stress yourself massively out over it, especially if you don't have risk factors meaning you're more likely to give birth early.