I can't feel if my breasts are full

The baby is gaining weight and dirtying diapers. He seems satisfied when he feeds. If I press my nipples, milk squirts without fail. But I have had a hard time getting any stock going through pumping and while my breasts are huge and heavy I can't specifically feel if they are full or empty. Just switch the baby from one side to another after 15-20 minutes of nursing. Haven't leaked even once. It all makes me wonder if I am producing enough at all.