I am scared that I am gonna die

I am 21F, I am overweight and I have been my whole life. I used to be around 90kg, 165cm. It has been a terrible year and I gained a lot of weight and now I am the heaviest I have been, 105kg. 

I am literally so anxious I am going to get a heart attack because of how heavy I am. Any time I eat, I get nauseous and lose appetite because I worry I am going to gain more weight and d.ie. I don't have high blood pressure but I do have thyroid issues that I found out about this year and they make my heart beat faster sometimes. 

I also get dizzy often. 

I am scared i will get a heart attack and di.e. I don't move much, I have terrible social anxiety and lately I have been very depressed too, I do leave my house at least once a day to walk my dog but usually I don't do much other than that. I don't have a job yet and I only go to school once every two weeks so I barely move. I try to work out but usually I only do so once or twice a week. 

I am really so scared I will di.e.