I'm so very sorry for you and i know from experience how hard this must have been for you.
Just in may this year i had to have my beloved 14 year old Heidi PTS and i can honestly say that it just about broke my heart..it was THE hardest thing i have ever had to do..but i knew it was the right thing to do..i loved her so much and could not have watched her suffer in any way..i did feel guilt of course and doubted my decision..did i let her go too soon?..but i think i was right in letting her go when i did, her breathing was laboured and she was exhausted from not sleeping i couldn't watch her struggle any longer.
MY heart goes out to you and your family and if you need to chat you are welcome to PM me anytime.
Kerry.