Yeast is treatable (oral thrush) and you should see your doctor in case you need medication to treat it. What is much more commonly associated with white coated tongue is poor oral hygiene. Smoking, alcohol use, what you eat and dehydration also can lead to it. Here's a full list. https://www.healthline.com/health/dental-and-oral-health/white-tongue#causes. See your doctor if you think it is yeast. If you performed oral sex, it could be gonorrhea (not if only performed on you) and chlamydia really isn't transmitted via oral sex. Oral herpes happens but white tongue wouldn't be the symptoms you'd encounter. Hope that helps.
Oral sex exposes you to gonorrhea, syphilis and herpes. Whether you feel symptoms or not, it's always good to test. At this point, if you test for gonorrhea and syphilis, the result will be accurate. For herpes, it will be necessary to wait until the 90th day after the exposure.
All the best.