I’ve been diagnosed with Strep but my test came back negative?

I’m a 20 year old female. I get sick maybe once a year and it’s usually just a cold. I’ve been diagnosed with Strep but my test came back negative. This happened around the same time last year as well, also a negative test result. I’ve been on antibiotics for over 48hrs but have had no change in my condition. My throat has actually began to feel worse. My tonsils are swollen but I have no visible pus or stones on them. I’ve been throwing up any meals I eat that are larger than just a single banana here and there (I NEVER throw up. I’m cursed with some sort of stomach of steel that would rather I suffer through a belly ache for days rather than just getting whatever the problem is out). I’m still getting cold sweats and feeling slightly feverish. I was prescribed Amoxicillin 875mg twice daily. Picture attached of what my throat looks like today