On my Tamagotchi Plus Colour, character Marotchi has died in my care at age 4, on 21st of November 2013 at an estimated time between 00:00 and 07:40.
You must take better care of your Tamagotchis.
You cannot continue under these circumstances.
But maybe this is just a mistake.
You should start again, and pay greater attention to your pet's health.
If you want to continue with raising your TMGC+C, then you will be on constant watch and mate it at 10 years old.
This is a downhearting disappointment but you can always do better next time.