I'm afraid we can't help with mental health act issues.
It doesn't sound like you have been given a date for moving from DLA to PIP yet.
So probably at this point the best thing you can do is familiarise yourself with our PIP claims guide and then talk to your health professionals about whether they would be able to provide supporting evidence when you do get an invitation to apply for PIP.
Being prepared for whn it does happen will make a big difference and hopefully will help you to worry less about it.
Good luck,
Steve
Nothing on this board constitutes legal advice - always consult a professional about specific problems