Can c diff infection happen on it's own without antiobotic use?

Yes: Although the use of antibiotics is most commonly associated with c diff, if you have exposure to c diff you can acquire it, typically in nursing homes or hospitals, affecting those people who may already be sick or have many medical problems.

Very unusual: Typically antibiotic exposure is required for c diff to take hold in the colon. There are many reports of c diff occurring after just one dose of antibiotics! c diff occurring without any exposure to antibiotics may be theoretically possible in some situations, but is very very rare and is unlikely to occur.