I keep gaining weight although I'm on a diet, what's wrong?

Anonymous
I started to have problems with my weight 5 years ago when I was 17. Since then, I have gained a total of 90 pounds. :( Weighing now more than ever, 218pounds. I haven't been on a diet all the time coz somehow I don't really notice gaining weight, I've found it out when I've gained like 20 pounds from where I used to be.. usually I only notice it from my clothes shrinking and needing to buy larger sizes. Then I decide to do something and drop some of the weight but I gain it back really fast! Like it can take me two months to lose 5 pounds and then in one week I gain it back! :(

Now I've started to see I look huge, too. I can't find clothes from normal shops anymore. My back and knees are hurting and I'm tired and sweating all the time. :( I've been on a diet for 3 months now but I've only gained weight 4 pounds!!! I'm so freaking out coz of this i'm worried there's something wrong with me and i'll just gain and gain?
I keep gaining weight although I'm on a diet, what's wrong?
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