Antibodies

I am questioning my body. I have been sick with a sinus infection for a week. I have been getting this about 4 times a year now since college. Am I really getting a different virus every time? Don't I have an immunity built up yet? I am taking antibiotics now because my own body did not get rid of the infection fast enough. But they do not seem to be doing too much.
To be perfectly honest, I think "antibodies" sounds very negative toward our body and not toward the disease they are trying to kill. They should be called "antiviruses."