Common Variable Immunodeficiency Support Group
Common variable immunodeficiency (CVID) is a group of 20-30 primary immunodeficiencies (PIDs) which have a common set of symptoms but with different underlying causes. CVID's underlying causes are different, but the result of these are that the body doesn't produce sufficient antibodies in response to exposure to pathogens.
If you have a concern you should get tested.
Some of the best PI docs came from the HIV/AIDS war. They understand the immune system and understand antibiotic therapy.