Hey Louisa,
your thoughts and feelings are perfectly normal, and for a lot of us losing our hair is confronting, it's ok to shed some tears. I know I did knowing I'd lose my hair that I had been so attached to all 52cms of it, I cried when I got it cut short in preparation when chemo started, but within a week I'd gotten used to short hair and then when I lost it, oddly it's been liberating, I thought in part my hair made me was who I was, but it's not, after being bald for almost 6 months now I'm still me! ?? and you will still be you!
try not to deal with the whole mountain in front of you, just focus on each step of this steep climb one at a time, you can and will get thru. Xx