I'veead that you can't overfeed a bfing baby, but my little guy has put on nearly 3lbs in his 3.5 weeks of life. This sounds like a lot, especially when I was fully prepared for him to lose! Is it normal?
You are obviously doing a great job well done. Both of mine gained weight like that for the first while it did settle down though. I used to get all the jokes about Jersey Gold top etc. Neither of mine lost either they just gained and gained.
My LO did this too, I couldn't believe it. She was small when she was born (just 6lb) but she never lost any of her birth weight and put on a lb per week for the first 4 weeks of her life purely on breast milk. At 5 months, she's now up in the top 2% of the growth chart (98th centile). It's unlikely there's anything wrong with your LO but I am not an expert so to put your mind at rest it might just be worth mentioning it to your HV. However, my DD was exactly the same and she's definitely healthy and happy!