I'm going to ignore this boy who is in love with me
Why would you ignore him?
I've already had my heart broken. I don't want him to have his heart broken by me
You should at least be honest with him even if you don't want to date him. It'd be rude to just ignore him.
I know I should, but I just don't want to deal with him.
I know it is hard, but you need to be clear with him that a relationship with you aren't in the cards. It is wrong to keep him hanging and hoping that there's a change with you.