I just bought the treatment of yeast infection of the pharmacy. He says to use it before going to bed. Why? Will it cause any problem if you use now?

I have my first yeast infection (boo!) I’m noticing a small stream very light pink and a few drops of blood. And ‘yeast infection or treatment? I’m not pregnant, and I’ve been with my partner for three and a half years – for STD are discarded. Any ideas?