This may seem ike a strange question but how do I know if the baby is empting my breast all of the way

It's not a strange or stupid question, for me before I breastfead my breasts where full and as my baby was feeding I applied warm towels, massaged and as long as you hear baby gulping obviously know baby is eating. I went about 15 minutes on one and 15 minutes on the other until baby was eating faster and sucking harder... went down to a 15 - 20 minute feeding.

After the feeding I noticed relief and that the breast was much softer to the touch... there really isn't any way to know if the ducts are empty (or unless you don't hear gulping and the babies mouth moving in a swallowing notion) but as long as baby is eating well and your producing... there shouldn't be a problem.