I had sexual exposure with a a escort. we did deep kissing , and she did oral on me without condom. while going further with vaginal intercourse, the condom slipped , which we came to know little later. but there was no pre-cum or intercourse during that period.she found the condom stuck in her vagina while urinating. then i used second condom and carried out pre-cum and intercourse. after 20 days of this exposure , carried out HIV1 abs and western blot , the test turned negative. is this confirmative ? if not when the next testing should be done and what type ? how risky the sexual encounter is ?