I've been hiding my health problems from my family.
Why are you hiding your health problems from your family?
They would try to make me change my way of living. I know they want the best for me, but they don't understand how things work in my world.
You may not think your family understands your situation but they deserve to know what's going on with you. Tell them the situation.
They won't understand. They don't know what I'm going through.
How would they know if you didn't tell them about your problems? They're going to know about them eventually so you should better talk about it now. There is no harm in letting them know.