Joanne,
I used to have a similar problem with my son, now 3 yrs 3 mths old.
He was ill every 6 weeks and worsen to more frequent "colds". He also seemed OK except having a runny nose. He used to wake up, before 1 yo, 7 to 8 times a night but NOT for feeds. Before 2.5 yo, he woke up 2 to 3 times, always at 12 midnight (like an alarm) and then somewhere between 2am to 4am.
Even as a baby, he seldom slept for 10 hrs TOTAL the whole day.
I found out the hard way that he was allergic to milk. That's why he was having "colds". It was actually his reaction to milk allergy. Because he was allergic to it, he was not digesting his milk properly and he woke up at night time. As he grew older, he had more solids and less milk, he woke up less frequent but still woke up at night.
We cut off all cow's milk and then started on a special diet recommended by the nutritionist to start healing his guts. Within 2 months, he slept for 8 hours and now, 7 months into his special diet and NO milk, he v v often sleeps for 10 hrs at night + 1 to 2 hrs afo naps.
You may wish to get his blood tested for any food allergies.
Rgds
e