There's this guy who I've been seeing lately, and I really don't want to tell him that I'm not interested in him anymore.
Could you explain to me why you don't tell him the truth?
I'm afraid to be honest about my feelings.
I understand it can be difficult to be open about how we feel.  But it's bad to lead people on in relationships and can end up with them being hurt.
Oh well I'm going to be honest with him that I'm done with him.
That's good. You should always be honest and let people know when you don't have feelings anymore. That helps them move on, as you already have-- leading them on would just ruin months of their life.