As you probably know, the psychiatrist is really interested in just one thing: mental
competency. Not the total absence of any type of mental illness: at the very least, most of us are a bit neurotic!
In short, mental competency is situational: it's always in relation to the situation at hand. So, relating to assisted suicide:
Do you understand the situation?
Do you understand the potential consequences?
Can you understand and retain any information about the subject that you've learned, or is presented to you?
Based on this information, can you make a decision?
Can you communicate this decision?
Based on all your posts that I've read, you're competent!

You should have no problem with that part of the process.