Breastfeeding

Elizabeth
I need your help ladies! My son is one month old and I'm breastfeeding him, the thing is for the past few days when it comes to feeding him he cries for a good 15 minutes or so before he latches on. I have to use a nipple shield and that's been working so I'm really confused as to why he cries when he's hungry and in trying to feed him. ..any advice /suggest will help!