Well, either 2 things...
you have a weak immune system.
Or before army you led a life away from others and tend to be a
"clean" person.
The trend i noticed in army is that my recruits who frequently get
sick is that they are usually from middle to higher income
families, stay in air con rooms, have their personal bathrooms, and
eat richer or home cooked food.
These people usually do not develop immunity that well than people
who, eat any food prepared by anybody, shares bathroom with the
entire family.
therefore, once in the army, exposed to communal settings, their
immunity naturally cannot copy well with the degraded
conditions.
first is, army things are never cleaned with detergent/soap (your
bunk floor, toilet bowls, mops). Your bunk area cleaning is wiped
by the same rag they use to wipe toilet bowls, they are never dried
properly so bacteria grows well....
so you are exposed to these things....
