A little background for context here. Jack got off to a slow start, he wouldn't latch on so the MWs in hospital advised using nipple shields, saying that my nipples were a bit flat. So we used shields. They hurt like hell as they were prone to slipping as he got hold of them, but he did start feeding. After a few days that stopped being so effective so we introduced expressed milk through an oral syringe in combination with the shields and he seemed happy to feed every three to four hours for a few days. But he had lost almost 14% of his birth weight by day 6 and so we introduced expressed milk in a bottle with a teat, figuring that the shields had already caused nipple confusion so there was nothing to lose. That was great as we could really see how much he was taking and 24 hours later when the MW returned to weigh him again he had gained 120g That evening he latched on without a shield! It was like a switch was flicked and we both suddenly "got it". He continued to take ten minute feeds every three to four hours for over 24 hours and it seemed to be going very well. The next weigh in 2 days later and he had gained another 80g. Then he seemed to find it more difficult again, since yesterday he fusses around the nipple, if anything being too eager and lunging at my boob without taking enough of it in! When he does latch on well he feeds fine for a few minutes then drifts off. He will start sucking again if I stir him but drifts off again very quickly. He does seem to be sucking, his jaw will be going, but I don't hear him swallowing so I'm not sure he really is drawing down much milk and may just be comfort sucking in his sleep. The upshot of this is screaming for food minutes after putting him down. We had a rough night last night with him seemingly hungry right through the night despite spending several hours total at my breast. I've heard people mention tongue tie. Could this be the problem and if so what is it?! Thanks in advance.