Why would I stop something that was helping?

"
Because it's not actually helping!  If it was helping....things would be better and you wouldn't have to do it anymore."  Hadn't something been said already about crazy people doing the same thing and expecting a different result?  He wasn't going to point that out to Brigitte.  For one she wouldn't care.  Also, he was the one who insisted on talking to her like it would ever do any good.

“I’ll do it again if I need too."

Well then. He was going to have to tell. That was all there was to it.  As her friend, as a prefect, as Walt.  Now, who to tell he didn't know.  His head of house?  Hers?  Eph?  How was he going to start that conversation?  Your gi-Brigitte is self destructing?  Hey, not only is she not pregnant, she's also not killing herself.  Good news all around.

If you think it’s a problem, stop making it so I feel the need to do it.”

Walt drew back as if she'd struck him.  "I...I'm trying to help you."  He said uncertainly.