According to my "clinical support system" (it's a bit like an autopilot), anything up to 8 a year is considered normal.
The problem is one cold sometimes runs into the next, and they tend to linger on and on, making you feel pretty lousy.
Most symptoms can be treated at home, and are medically insignificant. Knowing when to seek help is the trick. I'll try and post a link to some patient information websites.
Try
Prodigy or
the no hope service . I use these regularly- the info appears quite reliable.