Should I let him go or keep trying

Okay so there's this guy we've been off and on together for a while and I like him a lot ! But he's always saying he doesn't know if we will ever get back together, I've been there for him since I've met him he knows my feelings towards him but won't do anything. Should I just give him space and move on or should I do what my heart says and keep trying and just wait for him ?!?