Sugar Daddy. 💸

I'm an 18 year old girl, single and I've been going out with this 45 year old, single man who's a sugar daddy. 
I get paid £250 every time I go out with him, normally we go for dinner or to the cinema, I've never been to his house or been in his car, we always meet in public, yet I'm ashamed of what I'm doing, I haven't told any of my friends... 
I'm using this money to save for university and to make sure that I know I'll be able to cope when I have to quit my job to live in university. 
Does anyone have any advice on how I could or even if I should tell them?
Thanks X 
Re- I have a job already, it is a "legit job" yet it doesn't pay as much - ie minimum wage because I'm 18. Scholarships aren't an option as I'm not as intelligent or diverse enough to be granted one. 
X2- I'm only ashamed because it doesn't seem to be a "normal job" I know I make this man happy just by spending time with him and I'm not ashamed of that 🙊