Since you had unprotected oral sex, you were exposed to herpes, syphilis and gonorrhea.
Those spots could be due to a STD or they could be juts because of the physical action of having sex, as skin on that area is really sensitive. Syphilis is normally visible on the place of infection, because of the chancre, but normally there is just one of them. It could be herpes as well. As we cannot diagnose you, you should test as follows:
-3 weeks after the exposure, for gonorrhea.
-6 weeks after the exposure, for syphilis.
-3 months after the exposure, for herpes.
All the best.
If you have blisters now, you should get to a doctor and ask them to culture them. If they think it's herpes, make sure they do a type specific culture.