Im 3 weeks late..Ive taken a test..but it's negative..?

Tomorrow I'll be three weeks late and ive taken everyone's advice and taken a test so that if I was pregnant my baby could get the help and care from a physician as soon as possible..It turned out negative. I have no idea what to think right now..Im never late and I heard stress wouldn't even delay it 3 weeks...Ive never been on birth control and i don't do any athletics..Please I need all the advice there is..Thank You in advance.