How does antibiotic resistance happen? i've been on numerous ab for repeated uti as a child,and a few times for ear infections more recently.

Mutation and Change: Antibiotic resistance occurs because the bacteria find a way to survive. Through genetic mutation a few become tolerant to that type of antibiotic and survive. The bacteria evolve to continue there journey through DNA changes in their mitochondria or the cells energy center. They are programmed to do their thing and survive. That is why over use of antibiotics is so concerning.

Depends: Essentially using antibiotics frivously can cause bacteria to become immune to antibiotics - and hence they become less sensitive

It's the germ not U: Your prior exposure to antibiotics does not make you resistant to antibiotics. Any effect they had is long gone as are the germs you had back then. Germs mutate just like animals or us. New strains emerge that figure out a way to ignore a specific antibiotic. You might encounter a germ where the 1st abx does not kill it & another is needed, but that is because they changed, not your body.

The strong survive: Antibiotics will kill most vulnerable bacteria. Some bacteria will survive by either activating genes or developing mutations that provide antibiotic resistance. Repeated exposure to antibiotics, especially in the short term, will increase the odds of antibiotic resistance being common in the natural bacteria in and on your body.