W.T.
My little one got very squirmy and distractable around 6 or 7 months. She is now 10 months and it hasn't improved one bit. I find that she does great if I nurse her right after her naps. I leave the lights out and the door closed so she isn't distracted.
Doesn't really answer your question but keeping him calm and having fewer things for him to get distracted by will help. I know it's not always easy to lay down to nurse.