help me find a manhua~~ about a girl taking a mysterious pill

im looking for this manhua where mc/fl is a girl with brown hair, shes naturally conventionally "unnattractive" & on the chubbier side but she takes this pill which makes her skinny and conventionally pretty but she only becomes skinny on her period, but other times she just looks like her natural self, and everybody around her doesnt notice shes changing appearances and only notice her current self, and ml is looking for his lost love who is a girl who drew this sunflower painting, which fl painted, and the sunflower painting was unique cuz one of the petals were green or smth? ლ(´ڡ`ლ)