Do some massages to help baby to latch on easily. How often is baby latching? How many minutes? At least maintain 15-20mins of latching, your milk could be block that's why your baby isn't able to suckle longer. Massage ur nipples to open up the milo pores. cup your breast and roll the breast. it helps to soothe the flow easily. Secondly, try a bottle of hot water and roll over ur boobs.
perhaps u can try massaging them in circles before hand expressing it so that it's not too "hard" to squeeze the milk out. u should be able to find useful videos on youtube. would suggest u to get a pump asap else it may lead to mastitis. i had ever went so engorged that it took me 2 days of frequent pumping to get rid of the swollen lumps in the breasts.