i agree it is pointless to ask him to get up and watch you breastfeed although i totally remeber that lonely misreable feeling.
think of some things he could do instead, like letting you have layins at the weekend, giving baby ebm one night a week when he doesnt have to get up the next day and def ask him to do housework, cooking, chores etc etc
it took dh a LOOOOOOOOOOOOOOOOOOOng time to begin realise what it must be like to look after a baby 24/7 - he simply didnt understand, and I had to be quite specific about what I wanted him to do - then he would do it, because he realised that was his role.
i bet if you ask him about the headphone thing he will say that he thought his voice would disturb feeding or something - again, you have to TELL HIM that if he wakes up in the night and you are sat there feeding looking fed up then a quick word or an encouraging smile might be appreciated.
Honestly - my dh would ahve to be TOLD all of this, and then would do it, but he wont guess if you just keep it all inside
apologies if you have told him all this and he is just being inconsiderate and lazy - but it's worth giving him a chance to show you he isnt those things