First know that its not your fault and many transgender people have this.
You likely felt from an early age on something was wrong with you.
First you felt who you really are.
Then someone came along and told you you have to be a girl.
You didn't want to disappoint them, tried to see what they unconsciously expected and tried to adapt.
So there may be this feeling inside of you something is wrong and you need to hide.
Its possible you show other people a mask, and are afraid they could find out its not really you.
I'd suggest:
-relax. You do not have to adapt. People will like you just as you are. You are completely ok.
-if you are sensitive you should feel inside who you really are. Dare to show it, more and more. It will set you free.
Most people will be accepting and see its the real you. Those who are not you can avoid or just be persistent with them.
- You can train this. Nobody will do you any harm, its all normal people. Just go out, feel yourself, be friendly and people will react likewise. Over time you will come more and more into who you really are.
Just go out, enjoy yourself, feel yourself.
You can also train to talk to people slowly.
Saying hi to the cashier ... she probably will smile and say hi too.
Then as next step you can make a few small remarks ... if its late saying you wish her a nice evening, and its not much longer until she has off ... she probably will laugh and say she looks forward to it ...
later making small remarks about things you see ... just talking to people ...
its not difficult, just be yourself, and over time it can be fun.
Concerning your grandparents it might be an idea to come out...
maybe your therapist could help you, and here are a few materials :
https://www.susans.org/forums/index.php/topic,208438.msg1847638.html#msg1847638And some people come out in a letter, and show some materials later ...
hugs