What if I purposefully distant myself from boyfriend when he has suicidal thoughts?
Do you really think that's the best way to handle this?
I just don't want him to bring me down.
It sounds like he's having a rough time.  You should support him when he's going through stuff like that.  Otherwise, he might harm himself or end up leaving you!
I don't need him to be around me.
If you don't love him anymore, you should reconsider the relationship, but leaving him now would be cruel and heartless. You should first strongly encourage his to get into therapy. Get close friends and relatives involved if need be.