Young and lost 50% in the last 6 months

[Preston]

Hello everyone .
First my english is not as good as I would like it to be so sorry if there are any mistakes .

I'm 25 and in the last 6 months I've had an intense and diffuse loss of hair , accompanied by pain in the scalp , sometimes the pain was so intense that even wind would hurt me really bad and I couldn't even touch my head , now the pain is better but still losing hair ( less I think )
I saw 2 dermatologists , the first one told me it could probably be AGA and I should consider minoxidil , I didn't want to believe him because I've always had a lot and strong hair .
I moved and now that I live in another city I went to see another one ( seems to be a good one) that looked at my hair and told me it was AGA because my hair look better in the rear part and told me to take finasteride .

My first question is :
Is it possible that my hair loss could be stress related ? I'm actually living a very difficult personal situation .
Is there a way to be 100% sure it's AGA ? the pain that I've had makes me doubt that , even if my doctor said it was because of the hair loss .
Or maybe the stress triggered something that would have eventually happenned anyway but just sooner and stronger ?

2nd question :

I'm having some serious concerns about the side effects of finasteride , particularly after reading some stuff on the website propecia side effects .
I don't know what credit to give to what's said there , the dermatologist I saw said he's been prescribing this drug for like 10 years and never had any major or irreversible problem .