I hope things are working for the best for everyone
Everyone has given you plenty of great advice but there is one thing that sticks out to me. The fact that you started trying hard to change yourself when bubs was born. This is wonderful and good on you for doing so but your wife may be jealous or put out that you can do this for your DD but not for her. She could be wondering why she wasn't important enough for you to change for, this could even be the reason why she started to lose the weight and kinda explains her attitude towards you. Sounds silly but I can almost relate.
Congrats on changing and I hope things are becoming happier in your household