I have never tried your combination, but according to a quick internet search, your dose would not likely to take you to a place where you want to go, if they were taken separately.
I don't know about drug interaction and it's so hard for me to research about it, as I'm no expert on pharmacology or something like that.
Medication overdose is a notoriously unreliable method.
Forgive me that I send you a hug instead of useful information...
But there are several discussions on these drugs on this forum (please search for "Amitriptyline" on the search bar), which might help.
I have done countless times of overdoses in order to distract myself, mostly without suicide intention, only to get funny hallucinations. Unfortunately, a peaceful pill seems to be the Holy Grail for most of us.