any solution as my LO has been drinking milk and the milk tends to overflow from his mouth. We have changed various smallest size teats like Avent, Nuk and am currently using Mam.

You can try to hold baby up a little so that he is not lying flat. It could be due to baby kept on sucking and do not want to swallow. So holding him up with the bottle at 45 degrees, milk will flow slower as compared to lying flat with the bottle at 90 degrees.