1.) When you've been in past relationships and things have gone right or wrong but possibly have turned bad after a while and you turn out missing that significant other and wish you were back with them.
2.) Liking someone so much that just being in their presense for just a few minutes is satisfying enough to the senses.
1.) When Kerrie broke up with me I got love sick to the point that I called her everyday and sent roses, chocolates, and cards to her door.
2.) I think I turned love sick when Jenni came and sat by me during lunch today and I felt some sort of chemistry between us.