Milk coming in

Came in on day four. I'm currently using a nipple shield because my little man couldn't latch on ( he is eight days old) I have been trying to get him latched in but he freaks out and starts crying and moving his head like he's dying. ? so I give in to the nipple shield . I scared I won't be able to wing him off it. I hate the nipples shield is so annoying . And suggestion? Also I'm scared my milk wont last because I'm using the shield. I heard it can decrease your milk . I need help ladies what should I do?