To be lovesick means to suffer from an unrequitted love or deception.
Lovesickness has its own symptons, such as insomnia, depression, loss of appetite, loss of interest in everyday life and work, obsessive thoughts, mental intrusions and a frequent inclination to cry.
In the past, lovesickness was commonly recognized and diagnosed by doctors as an inhabilitating illness and received its own prescriptions.
In spanish lovesick means "mal de amor" and in latinamerican countries such as Colombia or Mexico it has its special celebrating day.
"I feel so lovesick that I will not be able to go to the office. I´m not in the mood even to dress up!"