help!!

I just turn 21 this passed May 27, and I’m more depressed then I have ever been in my life. I have always been a homebody, but for nearly two and half years I have not left my home to do anything except attend (college) classes and go grocery shopping. I get severe anxiety whenever I MUST go out in public. I am 5’7 an weigh 297lbs and I’m in need of moral support and guidance in at least losing 100 pounds. I have no idea where to start, but if I don’t do something I now, I know I will only get worst