The chances that you'd get an STD from protected sex is very low. There is a small chance that you could get herpes, HPV, and syphilis while using a condom, but it's very small.
Oral sex carries a low risk for gonorrhea, chlamydia, NGU, syphilis, anf genital herpes type 1 (if you don't already have hsv1), but again, the risk is low. Most experts don't think one act of oral sex warrants testing.
Symptoms for STDs take at least 2 days to appear at the minimum. Symptoms that appear sooner are usually irritation or an allergic reaction, etc.
No STD affects your sex drive.
I think testing will ease your mind.