I totally agree with Alisha, replacing the negative thoughts with positive\happy ones is the key. I dealt with a lot of anxiety many years back and I did talk to a counselor that helped tremendously. I had similar issues worrying about getting sick, and hearing other people's stories about being sick made it worse. I totally know where you are coming from. You also have to figure out why it started - for me I was in a bad marriage & felt trapped. If you could find a counselor that would be the best thing. I can also recommend a book that helped me a lot:
Amazon.com: Your Best Life Now: 7 Steps to Living at Your Full Potential (9780446532754): Joel Osteen: Books
This book talks a lot about thinking positive, and how your thinking can control the outcome of your future.
Feel free to PM me if you want to talk more.