I've been through this too. I was doing boot camp & still could not lose the weight but gained 10 lbs over the course of 1 year. And it was NOT muscle! So sick of hearing that excuse! It very well could be your hormones & I'm going to give you a few resources to start learning about it. You need to educate yourself & be prepared because not all doctors are understand or "believe" in hormone imbalance or they are quick to suggest synthetic hormones or an antidepressant.
I was tested for many of the things other moms mentioned including hormones. But my primary, my OB/GYN and the Endocrinologist blew off the fact that my progesterone was "a little low". And that was from blood tests. The World Health Organization recognizes saliva testing as the most accurate way to measure hormone levels. Some of the hormones in your blood are attached to proteins & cannot be used by your body. The blood tests cannot measure these separately but a saliva test only measures the "free hormones". Many women are told their hormone levels are "normal" based on blood tests which makes us feel - it must be in my head. Not necessarily true! Oh & "normal" is actually the average levels for women in the US - which may or may not be "normal" for you. Over 50% of women over the age of 35 in the US have to much estrogen (not enough progesterone) due to our environment, products we're using, etc.
This is just the tip of the iceburg on this subject. Here's where you can learn more:
www.drjohnlee.com Dr. Lee was the pioneer in this field. If you are able to squeeze in some reading, his book "What Your Doctor May Not Tell You About PREmenopause" is excellent. If you are local, I can also lend you a cd with a 1 hour lecture by him that is awesome. I have a hard time staying awake to read but I can listen to a cd while I'm running errands.
Hormone Balance: A Matter of Life and Health by Kristine Klitzke is another good book written by an R.N.
Even The Biggest Loser trainer, Jillian Michaels just wrote a book on this topic called Master Your Metabolism. She is far from an expert or a doctor but I think she carries a lot of credibility when it comes to weight loss. She has only discovered this "missing piece" to maintaining a healthy weight the last few years.
And my favorite "diet" is by Dee McCaffrey www.plandee.org She is an organic chemist who lost 100 lbs 17 years ago & has maintained it. So far I haven't read anything about hormones in her book but her eating plan is all about eliminating processed foods from your diet which is a huge part of what is messing up our hormones to begin with. When she explains how your body reacts chemically to certain foods - it makes complete sense!
As for me, I used bio-identical progesterone cream (not synthetic!) to get back into balance. I'm gradually incorporating Dee's eating plan into my whole family's diet because it's extremely important to me to raise them with the best eating habits possible which equals best health. I plan to ease off the cream as I reduce the sources of excess hormones & reset my metabolism. And I have lost 20 lbs, sleep better, feel better, handle stress better, etc. My doctor is skeptical but monitoring my hormones & progress with me. I suppose I could have switched doctors but maybe through my experience, he'll be more open to the next woman with these symptoms - I can hope!
I know this is long - there's so much great info to share - I hope it was helpful!