Is it ok to tell a man he is causing y heartache and tears at night?

well.. he is a close friend who is having a gf.. but somehow been using me ... lately uts all clear im being used and he has no intention to leave his gf.. at first i was at denial and took me long to realize things,, im crying at nights and hurt and depressed.. he talks to me almost daily... but whenever he asks me how im doing i just answer am gd great and start talking about my day and friends.. im wondering should i be letting him know how i feel, or i should b keeping things to myself?