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.

Is your baby latching? I tried Avent and had the same problem till we switched to pigeon teats. You can consider to let your baby try pigeon teats. The baby's mouth covers the entire teat when sucking and the teats are soft. You can read more about pigeon teats here: http://www.pigeon.com.sg/product_uri/bottle-feeding/