STI chances from brief oral ?

I had my first experience with a guy the other day, although to call it an experience in itself is a bit of a loose saying. I essentially gave him a brief oral for about 20 to 30 seconds, most probably less than 22 seconds if i''m being really exact! I trust him alot, and to my knowledge he hasn''t been with anyone since the last time he was screened and cleared for every sexually transmitted disease. To any extent, he''s recently become somewhat worried by some discharge that he''s having, so he''s told me to be aware just in case, which is fine, but i''m a very bad worrier when it comes to these things. How likely is it that I could have been infected from around 22 seconds of oral? And how likely is it that, after having been screened and having had little sexual contact since, that he could have anything? Thanks!