[...]
My concern is she may have read my diary, which has all my plans to ctb including the website that has the instructions. I've put some coloured sellotape around it that I have hidden so hopefully that would make her less likely to try.
You keep a diary where you've listed all your plans to suicide, and you think some sellotape is going to protect it?!
If you are serious about suicide, you also need to get serious about
not being detected. Keeping an unsecured diary is an
incredibly bad idea. Not only will it tip off your mother, but she can easily show it to authorities for the purposes of justifying you being committed to hospital involuntarily. If you
must keep a diary, type it on your computer or phone and protect it with a
secure password that you don't use anywhere else.
'Some coloured sellotape'. God help us
[...] Also I bought it nearly a month ago, so unfortunately I can't get it to go to a different address.
In most postal services, you can request a
redirection or
hold of your mail. It's typically used by people going on holiday or moving house etc. Might be worth looking into. You can typically request it based on the individual names of the recipient, rather than for the entire household.