Newborn not eating enough?

FTM, my son was born on the 8th and I feel like he's not eating enough or at all because when I nurse him he latches on and sucks but will stop and then start again every single time for very short periods and just fall asleep. He's not constant sucker and I'm also scared to death that I'm not somehow not doing enough for him. I've already got the baby blues bad and currently crying because  of everything. Support please!