Im currently on roaccutane and at my last appointment my dermatologist was calculating something after I had been weighed and said the next time I see you, you will be nearly at the end for your weight. Im assuming you can only have so much I think for your body - regardless of if you go private or not. Its virtually unknown to be on it more than twice, as its not worked you should see if you have any underlying conditions that is causing the acne to come back even after the roaccutane. I know a girl who went on it twice, came back and they investigated and found out she had PCOS.
Good luck, I know how distressing acne can be and treatments not working.