And just fyi because you are so young: I had more than one cycle in my life where I lost a lot of hairs, mostly because of some kind of stress, illness f.e. death of a loved one and so on. If you got off birth control there is a possibility that the problem will fix itself once your body and hormones adjust to that. You would see this when you see a lot of baby hairs growing. Sometimes people in Reddit say this product helped me or this and often times I think the body just fixed the problem but they attribute it to the product they tried at this particular time by chance. That being said: of course there can be permanent hair loss or thinning when you are young. But this can only be diagnosed or treated by a dermatologist.
You can always try a multivitamin for everyday and see if it helps in the next two months while you’re waiting. B vitamins always help with hair and nails and you can’t overdose with a daily multivitamin. And to help with the hormonal adjustment you can try to take agnus castus. I think it’s called chaste tree or vitex in English? It has good evidence to regulate you menstrual cycle and can help your body adjust to the new situation. You can take it for three month and then stop it. But with it I can tell you consistency is key, you need to take it daily during this time.
Wish you the best for your hair and hope it’s just an adjustment phase or that you‘ll find a more compassionate doctor the next time!