weight loss diet plan

I haven't been completely PERFECT on a diet plan, but I KNOW I am not awful either. My diet is low fat. Following Weight Watchers. (I have three children) What I am getting at is I am FRUSTRATED that my scale hasn't changed; nor have my clothing sizes. (one time) But I KNOW to treat myself once in a great while or you can REALLY fall off the wagon. And Vice versa. And yes, I know there are those of you that are completely against drugs; whether it be prescribed or over the counter. But in my case I need extra help. Has anyone taken anything. I am TIRED of failing. I am considered obese; though I don't necessarily look it. I drink plenty of water-some days MORE than 8 glasses (8 oz. I eat low or NO sugar things. I have also tried low/no carbs. I have been doing research on "over the counter" pills, and nothing really jumps out. I have been seriously thinking of talking to my doc about prescribed pills. Someone HELP. Sure, I have had my Shamrock Shake at McDonalds.