Are you using the WHO charts or the ones you get in the MCHN book? There is a bit of a difference to them as the WHO ones are based on breastfed babies not on formula like the book charts. Just google WHO growth charts. I would think though if he is having lots of wet and dirty nappies, is making some gains, even though they might be small, is otherwise healthy and happy that just because he isn't on the charts it shouldn't matter. Also now that he has hit 6 mths and will be starting solids you may find his weight start to increase a little more over the coming months. Sounds like you are doing a brilliant job and the only other thing I would suggest would be to try feeding in a quiet room, or with a blanket over you both so he doesn't get too distracted. I had to do this at around the same age with both as they were such sticky beaks they wouldn't feed right. Good luck hun and let us know how you go.