I think it all comes down to the skill of your ortho. Some orthos are not specialized to do linguals. I am going to the top lingual orthos in London, and the journey has been good so far. No complaints, and when I see patients at that clinic (The clinic only does linguals) they have picture perfect teeth. Maybe you can try other orthos??? (look at reviews from this board).
Sorry to hear that your treatments have been bad. Hopefully it works out .