Anxiety over doctor appointment

Here I am freaking out again.  I have to go the my doc in order to get my meds refilled.  I was only seeing him annually but his office indicated that due to the Quality of Care under Obamacare I now need to see him twice a year.  I don't even use insurance benefits under Obamacare!  So I don't get it.  Nonetheless I have to go.  I've had breathing problems outside lately.  I'll be walking and talking and all of a sudden I feel like I'm having palpatations and can't breathe.  And I have that awful post nasal drip and clogged sinuses which I'm certain is probably making it difficult to breathe outside.  Of course I've convinced myself I have lung cancer, COPD, heart issues or something horrible.  My breathing issuues haven't affected anything that I do but I'm still certain there's a death sentence involved.  I'm terrified he's going to send me to a specialist or for tests or something that will send me over the edge.  Luckily he's been my doctor for years and he knows what a basket case I am.  But I still can't help worrying even though my appointment isn't until Thursday.  I wish I could be like so many people who don't overreact to a doctor's appointment.  I hate feeling like this.  I've been doing better since my panic/anxiety issues went into overdrive a few months ago.  Now I'm headed back to where I was.  I had even cut out the Xanax.  But here I am again.  Ugh.