19 and losing my hair

I’m 19 and started to notice I was shedding a lot about six weeks ago.  In those six weeks I’ve lost probably half of my density at the front, and a decent amount at the crown. What the hell is happening? How can this happen so quickly, this is genuinely devastating. I have an appointment with my GP on Friday where I’ll be trying to get a fin prescription, but I don’t even know if fin can help. If the GP won’t give me a script I’ll probably end up having to wait 8-12 weeks to see a dermatologist, by then it’ll be too late I imagine.

See a doctor who has the HAIRCHECK instrument to find out exactly how much hair you have lost. I doubt that you lost half of your hair in just 6 weeks.  If your doctor prescribes you the drug finasteride, then when taking the drug you will know which way you are going, better or worse over time.  See here: https://baldingblog.com/2017/01/10/value-haircheck-bulk-measurements-two-patients-seen-today/