Lose belly fat after having a baby?

I am 19 I had a baby seventeen months ago. I feel so embared to be my age and look like this I have a big pooch over my belt line and stretch marks it looks horrible like a sack. I feel embared to get naked in front of my husband. I also got saggy after giving birth and my size went up from a D to a DDD. Not to mention my are as big as cup lids. I feel so bad about my body. All of my friends are slim and look good in bikinis with belly on rings. I tried dieting last summer and only lost 10 pounds after hours in the gym so i quit. Now this summer is coming up and im back to where I was. Im 5'4 and weight 170 pounds. How can I change this? I cant stick to a diet. Everytime i try to limit what I eat my head hurts really bad. And I have a baby so I cant go to the gym alot and also am in the process of going to nursing school. Please Help.