Oh hunni... It is abuse, both abusing you and your poor Mum. Lupus is horrible, I really sympathise - she certainly doesn't need the crap from your brother. Have you two spoken about it and what options there are? I hear that reporting things anonymously can easily be done through crimestoppers
Did the Dr give you the 50mg? I would suggest you start it for a couple of weeks and see how you are doing.
