You definitely have not STD. Burning on urination, without discharge is not a common symptom of STD; 4 months is too late for any STD to show up; and cipro would have cleared up most STDs that might have been the cause.
Clear discharge is normal during sexual arousal; everybody gets it (whether or not they notice it). (It's called pre-ejaculate fluid, or pre-*** in common vernacular.)
Stop checking yourself. There's nothing wrong.
Good luck-- HHH, MD