I made a thread like this a few months back because I've had the same problem. When working the corporate world I never got sick, maybe once a year. Since joining the airlines (2yrs now) I've had a cold just about every 2-3 months, and like once a year I get hit with something pretty hard. Had a bad sinus thing going on last year, and just a couple months ago I had a terrible cold with bronchitis that kicked my butt for an entire week.
We work in an absolutely disgusting environment, and I'm not a germaphobe, but NOTHING we touch is clean. We're stuck commuting in the back with the general public, walking through dirty airports filled with all sorts of people, and then spend days in a flight deck that hasn't been cleaned since the delivery flight.
My routine has been to wipe down the yoke/throttles and common knobs with wipes when I can (Not that it helps for more than a leg or so). I always wipe down my phone with alcohol wipes at the end of the day, and try to avoid touching my face. I also always throw on disposable gloves when I help to cross seatbelts at the end of a flight. Also, wash your hands!
TL;DR: You're not alone