I agree with Rhian. Do talk this through with your T including the part about your mum not wanting you to talk to your T about it.

I too think it is a good thing that your parents are making this effort. Since it understandably gives you cause to worry it is important you are able to talk about how it makes you feel. It is good you have your T. I wonder if your grandma couldn't help to reassure you or at least provide you someone else to talk to about how it is effecting you.

Wishing you well my friend.