Say if u had unprotected sex with someone who does not have any infected area/sore can u still get std?

Yes. The presence of a STD is not defined by a visible sore, although that can help. Many can exist in a carrier state in those infected and be spread to unsuspecting contacts. Chlamydia, HPV ,syphilis and sometimes gonorrhea can all be passed by asymptomatic carriers. Condom use can decrease risk, but is not fully protective.