My son doesn’t nurse for long the longest time he nurses is 7 min most of the time it’s 5 minutes or…

My son doesn’t nurse for long the longest time he nurses is 7 min most of the time it’s 5 minutes or less. I feel like he is not getting enough but spits it out goes to sleep right after breastfeeding so it’s hard to keep introducing the breast. I wanna give him the bottle after just in case he is not getting full.