Breastfeeding advice needed !!

Angelika

My little one is 6 weeks old tomorrow. After birth he has spend 4 days at the NICU due to his small birth weight (2kg) where he was first tube fed and then bottle fed (my breast milk ) as he couldn't latch onto my breast. Now he latches onto the breast but only sucks a few times and then let's go. ( so we always end up giving him a bottle with my milk ) Once in a while he manages to get a good latch and feeds for 15-20 minutes but after I take him of the breast he screams like he got no milk ( my milk supply is definitely high ) and then doesnt relatch onto the other breast as he is crying so much. Any advice to why that could be or what could help ?