B.,
First, it is up to you to remain healthy in every way and take care of your baby (and family). That being said, you have to take care of yourself emotionally - and if you have a network of girl friends, talk to them. A friend of mine once said she has coffee with a friend at least once a week, it is the best therapy. :)
There are books, there are websites, but nothing is better than people contact.
You are the shape you are, you are doing what you can. You are not being unhealthy about removing the weight, either, it sounds like. I would add talking to your doctor about being tired, too, as that may be something simple, like iron deficiency (anemia is NOT a girl's best friend!)
It is hard to have someone so close say and do these things, and to let them roll off your back. You have also come through the miracle of childbirth, and have been bringing up a beautiful person.
You need to take charge of your situation, or your little girl is going to learn this when she grows older. Gentle grace will help you - not getting mad, not getting even, but simply and quietly stating what you do and do not believe. It is easy to argue with someone who sounds like they just opened their front door on the wharf. It is not easy to argue with someone who keeps their cool. I know it is hard to keep back lack of motivation and tears when someone says something so personal.
From experience:
I do not believe I live up to anyone else's standards. God made __________ this way, and He made me who I am and put me where I am. I am doing what I can to be healthy while at the same time take care of my family. (Or I have spoken with my doctor and s/he doesn't want me losing weight so quickly - it is unhealthy).
Therapy is not a bad idea - it takes a while for some to get the hang of gently and gracefully standing up for oneself, and others just catch on quick.
I had to deal with this issue in reverse, my husband did not care what my weight was. I had to motivate myself to do what is healthy. It is HARD! It is much easier to have a buddy - even easier when that buddy is your husband - but that is not always convenient or possible. Once you depend on yourself to make food choices that correlate with supplementing your body with nutrition, rather than eating just because, you will see what will happen to your shape - and YOU will like it.
Above all, you do this weight loss for YOU and no one else, because if you are doing it for someone else, and they don't like your progress, or they don't like your final shape, or they don't like __________ then it will do you no good whatsoever. You are the person you have to see in the mirror every day, and you are the person who you have to answer to when it comes to health - do I feel okay today? Can I improve that? Do I feel like doing this? Can I do it for just a little bit, and see how it works out?
You are worth the time it takes to make good food choices, buy the food, stick to the food, keep other foods out of the house (if you have a hard time stopping at one butter oatmeal raisin cookie like I do), and be responsible for your nutrition as well as your family's.
You can do it! It's not IF you want it, it's WHEN you want it, and each day you make a good choice, it all adds up in a much more positive way.
Good Luck!
M.
PS: You are lucky it is only 40 pounds! AND that you have dropped 15. See I went down post baby, but I am right back up and beyond what I was before I became pregnant, and am almost back at my all-time high from 2005.