At which time (especially) can I determine if I'm pregnant? (i have 5 days of delay)

Pregnancy test. Current otc urine pregnancy tests approach the accuracy of those done by a lab. If you are indeed pregnant, a urine test done 5 days after a missed period should give an accurate result. If not, you can get confirmation by a blood HCG test (qualitative=yes or no pregnant; quantitative=how long you've been pregnant).