How could she not see it?

I woke up this morning, and my throat was killing me. I found a flash light, looked at my throat and saw a sore about the size of the tip of my pinky. After taking a few Advil, I called my doctor’s office, sat on hold then made an appointment with the nurse pratitioner. There are two doctors I see on a regular basis. Both are female, both very good. One of the doctors recently had a baby so it has been a little harder to get in, hence me seeing the nurse practitioner.
I was pretty convinced I had strep. I have had a headache for several days, not to mention the big sore on the back of my throat. I weighed and was shocked to see that I was at 134.6 which is an all time low for me. When the NP came in she said that the strep swab wasn’t showing strep. She asked me to open up to take a look and said she couldn’t see anything. I said, “you can’t see that sore at the back of my throat?” “There is nothing there”, she said.
So I swallow and it hurts. She gives me the typical “you have a virus/we don’t know what you have” answer and tells me to call in a few days if my throat still hurts. I leave and as soon as I get in my car, open my mouth and look in the rear-view mirror only to see the sore plain as day. WTF?
So to make a long story short, I’m a hurtin’ unit today. I can barely swallow and I am a little worried about the weight. 134 is low for me. It still puts me on the edge of a healthy BMI but I really don’t want to lose any more weight. People at work are already saying that I have an eating disorder (which I don’t. I just don’t eat much bad stuff anymore). If I lose another 5 pounds I will be underweight for my height. I can’t believe I am saying that when I was 45 lbs heavier in January.