Hey there Happypills! First of all, I can't say that I wouldn't be feeling the exact same way as you if I were in your shoes...so it may not be a great idea for me to reply to your post! (I have health anxiety....BIGTIME)
At any rate, I just wanted to say to you to relax! All will be fine for you! The doctor isn't going to find anything bad inside of you during the operation, and your lungs and everything are probably just fine! So, take a deep breath, and RELAX!
Best Wishes to you!