how do i know if it worked?

i caught something after having a one night stand and the symptoms were, itchy inside the tip of my penis, stinging feeling when ejaculating/peeing and slight clear-ish/off white coloured discharge ...i went to the dr's and i was given antibiotics. all symptoms have seemed to of gone apart from very slight stinging when only peeing, only some times ....my question is that can i be sure that the antibiotics worked? how can i tell?