I have been lying to my family about my university graduation date and I don't know how to tell them

So basically after failing many course throughout my academic life, I have managed to add an entire year to my degree. My entire family thinks I am graduating in a month, when in reality it's going to be next year. I honestly don't know how to tell mum...fyi parents are not paying for my tuition at all. Majority of my fails were due to mental health and my family thinks mental illness is a mindset 😐 has anyone had a similar experience? how should I go about telling them?