Welcome to 3FC! I've found so much support here that I absolutely love it, and I've barely scratched the surface of what's offered here. Explore it when you have a chance. It's truly wonderful.
The bad news, as you know, is that you weigh 300 lbs. The good news, believe it or not, is that you're 19 and you weigh 300 lbs. By starting today, you're giving yourself so much of your life back, and you don't even know it yet.
A dose of reality can be such a blessing in disguise. If you know where you are, you can know where you're going. (That sounds so cliche in my head, but damn if it wasn't true for me).
If you're up for exercising, come join us in this thread:
http://www.3fatchicks.com/forum/showthread.php?t=147747
I lost access to 3fc for a while, and counting my minutes kept me motivated, and I saw a difference even when I wasn't losing weight.
Welcome to the rest of your life.