Concerned Need Advice

I usually Have Normal Cycle But I'm 20 Days Late Last Time A Had Sex Was 27th May I Spotted On 3rd or 4th Was Only For 1 Day Haven't Bled Since Took Preg Test On 17th It Was Negitive How Long Does It Take To Show Up On Preg Test So Confused Duno If I'm Preg Or Not Plus First Appointment To Find Out Is In 3 Weeks 😢😢 Could Someone Please Give Me Wee Bit Of Advice To Stop Me Over Thinking xxxx