Cunnilingus is very safe sex -- with low to zero risk for any and all STIs, even if either partner is infected. That is, STIs rarely are transmitted from the vaginal area to the mouth, or vice versa. And no STI causes "white lesions" or "white patchy tongue". Most likely you have a garden-variety coated tongue, which goes along with innumerable minor medical conditions, like common colds. Your negative RPR proves you don't have syphilis; all syphilis blood tests remain reactive during latent infection. (The very definition of latent syphilis is occurrence of a positive blood test in absence of symptoms.) You can be sure you do not have syphilis of any stage. I don't advise any other STD testing either. Keep working with your regular health care provider if your oral symptoms continue, but don't worry about STIs.

I hope this information is helpful. Let me know if anything isn't clear.

HHH, MD