Thanks for writing and expressing your thoughts! I am really sorry about the situation you are going through.
I can understand what you are feeling when people hurt you about your fatness. Let's go one by one at your problem.
I see 2 things 1. You are fat and because of this people make a fun of you. 2 . you are introvert-which I suppose is a result of people making fun of you because you are a fat!
Well Abid, you have not mentioned about what you did to get back to normal,like exercising, following a proper diet etc. So I would suggest try using techniques to control your weight. Indeed if you are too fat, it hampers your health as well. Go to gym, walk for some minutes daily, have proper balance of vitamins and proteins in the diet. If your family is not supporting, you can do these things on your own. Have some friends with you while walking or exercising so as to generate motivation.
Regarding you being an introvert, well it's not an abnormal thing! But you can exercise talking to different people of various age, for at least 5 minutes, every week. Try to interact with new person every week. you can interact with them based on your topics of interest or better ask them about their interest and take ahead the conversation. This will help you to boost your confidence as well!
Apart from following diet, you need to pay attention to your thoughts as well! As thoughts affects mood and then in turn your digestion. It's okay to be sad but do not cling to it always. Have some positive thoughts and confidence in yourself. You may be having some good qualities, some interests, try to invest your energy in them! You will feel good!
At this moment, you need to be calm and stable. Just relax and think what you can do to control your weight and build confidence. I am sure you will find a way out of this!
All the very best!