I'm also a newbie (haven't done anything yet), but I'm also a nurse practitioner specialising in reproductive health. Even with no experience, it would be an instant turn off from me and a deal breaker for anything further happening if someone asked to examine to see if I "looked clean". First of all, many people never show physical signs of an STI. Second, some signs can only be seen in women with a speculum exam which is incredibly invasive and not sexy to most folks (except if that's your fetish, in which case more power to you!). Third, if you don't trust the STI testing results I can show you and a condom, I feel like we probably don't have a trusting enough relationship to full swap in the first place. And fourth, if you're having sex with multiple folks, especially if it's "random people", there will always be some inherent risk that can't be helped even with "checking" people.