Still gaining weight

Hello everyone,
First off, this is an old account, please ignore the details on my account.
Second, I'm not sure where else I can find information. I have attempted talking to my doctor and i've done blood work (all ok). I have been eating my recommended calorie intake with specific foods and excersie plan given to me by my doctor but i'm still gaining weight? I've talked with him again about it and he says to just stick with it and "eventually" i'll loss weight. I'm also drinking enough water. Whatsmore, I have a small appetite and if I eat more than 1,000-1,200 calories, I become sick. I do not consume soda, coffee, or juices (only water). I do not eat out and I keep an extremely detailed journal of everything related to my weight. I also do not consume candy or much salt. I should also add that i've had two children 3 and 1 years old.
Here are the details:
1,200 -1,500
Walking 10,000-15,000 steps per day 3x a week
No gains or pasta
2.7 liters of water a day
I weigh 240 lb and 5'6
I have been measuring my weight gain by inches and a scale.
Am I doing something wrong? I'm not understanding why i'm gaining weight. When I do searchs, I find that there is an even mix "you're eating to little" or "you're eating to much". Any thought or suggestions?