Alpaca, I'm truly sorry for the anxiety you are experiencing. I would agree, there's not much worse for us. The time between discovering and proving/disproving things seems like the slowest time passes, too. We just seem to find ways to keep calm, in most cases. In others, some of us turn to anxiety meds.
When I go through extended periods of being unable to breathe, it feels like I will die any second. I even fear sleeping because I have to consciously make myself breathe and I feel like I will drift off and not wake up. This has been going on for 2 years in December. I look back in amazement that I have endured this for so long but also to remind myself that I am doing fine. I have gone almost a full year with no anxiety meds, too, which surprises me more.
Find ways to occupy your mind and the time will fly by. I use cooking, gardening and politics, too, although the politics part doesn't bode well for relaxation. Hang in there and I am certainly hoping for the best possible outcome on your FNA.