No, you are not at risk for anything, and no STD would give you an upset stomach. (Stress would, though.)
Also, "tranny" is an offensive term. The correct word to use is trans person. I realize it's used a lot in sex ads, but there's no reason to use it otherwise. (Just a little FYI.)
Hi upset stomach is not a symptom of any std but could be from anxiety. risks for unprotected oral sex would be Gonoreah, syphilis and herpes. but from what you describe they would be quite low risk.