I'm so so sorry for your loss. And I'm really sorry you have to experience all this. I don't think your body is sick in any way, but all the anxiety is taking it's toll. You must be exhausted of all that happened to you.
One of my closest friends lost her dad when she was your age. She also felt like something horrible would happen to her. She was even scared to get in the car with her mom.
Try to talk about this at much as possible. I know you might be thinking your mom has been through enough the last months, and you don't want to bother her with your problems, but that's what moms are for! And I'm sure she really wants to help you. Try to be as honest as possible to your therapist. People can't help you if they don't know what's going on in your head.
To be honest, I think you have the right to be messed up at the moment. What you experienced is way too horrible to process in a few months. So give yourself a break. If there's something we can do for you, please let us know. And know you will be alright, but you have to give yourself the time. Take care of yourself and your body. You deserve it!