Re supporting evidence for pip

Hi I am on DLA indefinitely and I have started my PiP claim.First of all I was only asked if I had been hospitalised with a mental condition on my phone call, not do I have a mental condition.I suffer from depression. I was also asked how my name was on my bank card, this I couldnt remember . not sure why they needed this.
I was also asked if I received DLA and if I had copies of my forms and if yes ,I could send them with my Pip form, but not seen this advice so not sure if I need to send them
At this moment I think I cant deal with the stress of it all and I feel pressured .My form has to be in by the 10th of April and I have received a letter this morning to say they haven't got my reply and if I do not return it my claim and any entitlement may be disallowed.if I have returned my form in the last two or three days ignore this letter.
I was posting it this weekend, will this be on time?

Thank you so much

I had my home consultation appointment today by Capita. I was surprised as there were two of them,One was training.I was also told that the lady lived local and the other not far away.
My husband was present which was a good job because I was so stressed and nervous I could not answer a lot of questions
The thing that worried me most was the fact that I kept being asked if my medication worked and were most of my illness due to my fibromyalgia and diagnosed by a doctor or specialist.
I will have to wait and see what the outcome is,not sure if my nerves can withstand any more