I have been going to a tanning parlour for 20 years. Last month, my boyfriend noticed a black mark on my back and now he says it's getting bigger. He's really worried about it but I'm inclined to pay no attention to it, especially as I can't really see it. Is that OK ?

No! This could very easily be a skin cancer. They're common on the back and very often people aren't aware of how big they are because they can't see them. So I beg you to consult your doc this week.