lovesick 渴望爱的状态
A deep often depressing feeling of wanting to find love; to be longing for love; to be without a companion to share ones life with though it is desired deeply.

Crush 有强烈的好感/冲动在一起
a burning desire to be with someone who you find very attractive and extremely special.
My heart broke when I found out my crush was seeing another person.

infatuation 迷恋；痴情
Infatuation consists of people thinking they are in love but when indeed it is just a deep lust or like for another person.
Infatuation sucks.