Let me also add that it is not too common for this to happen, but its common enough that you should be aware of it and carfeul.
YES!!!! You can catch Herpes or the mouth, chlamydia, I believe syphillis as well. If you partner has had oral sex with anybody that has an STD or has kissed someone else who has had oral with an infected person, you can catch it as well. Do you think that you have something?