According to the it's Not Unusual Songfacts, this was written by the classical music arranger and conductor Les Reed along with Tom Jones' manager Gordon Mills. They wrote it for the British singer Sandie Shaw, but she turned it down. Tom Jones saw the song's potential, recorded it, and it became his first hit single.
It's not unusual to be loved by anyone
It's not unusual to have fun with anyone
But when I see you hanging about with anyone
It's not unusual to see me cry, I wanna die