It's up to you when you tell someone but I really would encourage you to discuss it when you are ready. As someone else said, it can give your T an idea of when you are struggling and help you start to work through it.

I'm sorry you are feeling abandoned by your T. I am really hoping that he has just been busy due to the holiday period. Do you have an email address or contact details? Maybe just send a quick email or call to alleviate your fears and let him know of your concerns that he has left?