Shaving for prom

Hi! My prom is coming up and I'm wearing a dress that shows my armpits..

I have really thick hair that, even after shaving or using hair remover cream, is still visible under the skin. This leads to darker skin on my underarms and generally just looking like I didn't shave!! It's so bad to the point where my mom literally vetoes tank-tops without a cardigan when we go out.

I feel like a hairy monster 99% of the time and I really don't want to feel like that on my prom night. Any help would be appreciated, except for solutions like laser hair removal or anything long-term like that!!

Thank you!!!!