I'd say about two or three times a year. Sometimes, I get sick when the seasons change. Most of the time, I just catch the cold from someone close to me when he/she is sick.
It's more my allergies during the spring. >.<
Otherwise, strangely immune to a lot of illness even if there's a minor epidemic on campus, 90% of the time.
Does being so constipated that you have to make regular trips to the local pharmacy for pills to help keep shit flowing or else you'll end up in the ER count? (Keep in mind that the mandatory ER trip thing was learned the hard way) cause if not then I'm never sick. Ever.
From my early years 9-17 I would get sick for (weeks/months) :( and I would have brief periods of time (maybe a month or so) where I wasn't sick. But ever since I gotten in my 20's I get sick maybe 4 times a year.