How Long After Sex is it GUARANTEED, that you are STD Free?

Patient: How Long After Sex is it GUARANTEED, that you are STD Free?PLEASE READ DETAILS: I had sex with a girl about 8-9 months ago, and wore a condom. I just found out today that she has 4 STD’s. (she could have gotten these in the past 8-9 months from someone else) However, I was tested for ALL STD’s 2 months ago, everything came back NEGATIVE. So as of right now I have NO STD’s. But how long after this sexual experience can i be SURE that I am STD free???

Doctor: