What should I say to a guy I dont like anymore that I'm dating that I want to break up with....how should i say it?

"I've only been thinking of you as a friend lately, not a boyfriend."
There's a base to work off of; add whatever else you'd like to say. It gets the message across that you don't like him in the way that you should in a relationship but that you don't hate him. In private, alone, rip the bandage off quick, don't let it get drawn out, say it clearly, make sure he understands what you're saying fully. My similar breakup lasted an entire week because I didn't say it clearly enough.