Has your kitty always acted this way, started doing over a period of time, or is this something that has developed suddenly? As TeriM stated, it would be a good idea to take the kitty in for a complete check up in any case to rule out a medical reason. If indeed it has happened suddenly then yes, a vet visit most definitely is in order.
It is possible your kitty is suffering with separation anxiety. Here are a couple of sites for you to read. Maybe they will help you figure it out. As noted they also recommend a vet visit.