I have a 9mo who was having poor weight gain. Actually we were to the point of weight loss, muscle mass loss, milestone regressions, and increasing lethargy, nursing more then 35 times a day. Childrens hospital didn't/wouldn't believe a lip tie could cause those kind of problems, that the frequent nursing was behavioral and everything else was from limited solids, they were ready to inpatient her and put in a feeding tube. We had the lip tie cut and used some donor milk for a week while i rebuilt my dwindling supply. She gained 6oz in a week and a half. She has regained all her milestones except speech in that week but will begin working with Early Intervention next week for it. She does have a PTT but Dr Kaplan (stoughton Ma) didn't feel it was tight enought to be causing the problems we were seeing. Childrens still won't and doesn't believe there was a correlation but how could there not be!!!
I would try to find a dr that uses a laser they tend to be a better option.