Mother of 3 needs help losing baby belly before it ruins my marriage...?

I am a mother of 3 great kids but they really did a toll on my stomach. I am 5ft 2 1/2 in and i weighed 135lbs before I got pregnant the first time at the age of 17 in 2003. I gained 50 lbs with my 1st and had her when I was 18 in 2004. I lost 20lbs and about a month later I was pregnant again and gained 30lbs and had her at the end of 2005. I was extremely depressed during 2005 because my husband was deployed to Iraq for a year. When my husband returned home in 2006 I was only able to lose about 15lbs. Then surprise I was pregnant again in 2007. I was sick the whole pregnancy and on bed rest for most of it so I gained 20lbs and my son ended up having to be delivered 2 mths early via C-section and at that time my tubes tied. But here is my problem.... with the stress of staying at home with 3 kids and my husband being medically discharged from the Army and out of work, I haven't been able to spend a whole lot of time on losing weight. Now my marriage is on the brink because my husband, being in shape from the Army, thinks it is easy to lose weight and that in 3 years my baby belly should be gone already. In some aspect he could be right but I'm stuck at a plateau. I'm not gaining weight nor am I losing weight. I'm eating right, exercising when I can and nothing is happening. If anyone has any advice please help me. I have been through way too much to lose my husband of 7 years and the father of my children over 30lbs.