Yes, receiving oral sex and sex with a condom can both increase instances or the severity of a yeast infection. Both activites increase the warm, wet environment that yeast grows and multiplies in.

Yeast infections are also called candidiasis or monilia. A YI is caused by an overgrowth in the vagina of a yeast-like fungus normally present in the body. A woman with yeast vaginitis may have a white, cottage cheese-like discharge and itching or burning which can be so intense that it interferes with sleep. It is usually treated with antifungal vaginal suppositories or creams. While yeast infections are more common in sexually active women, many women get these frequently and they are not related to sexual transmission.

one other thing you may want to use as a yeast infection preventative.
cleanliness...

make sure that before you touch yourself down there or before someone (or something ie. a penis) touches you that it's clean. cleanliness is like an insurance policy against getting yeast infections. make sure to wash your hands with soap and warm water before changing tampons, etc. as well as afterwards.

good luck!
jasmine