I recently had sex with my ex and before him I tested and was clean, we had sex about a week ago. How soon can I test to get accurate results?? (For STD) for it to show up IF he was lying to me/

I asked him when’s the last time he went to get tested (b/c it’s been a year since we hooked up) and it’s like I caught him off guard and he sounded like he freaked out and just threw anything out there, which is why I’m worried now.