Delays in your period can be caused by a variety of different things. Pregnancy is only one of these. You may of tested too early and if this is the case, I would recommend you perform a HPT 3 - 4 weeks after you last had unprotected sex. Alternatively see your Doctor for a Quantitative beta hcg pregnancy blood test which can be performed now. It is 100% accurate.
No
Yes
No, a period and a negative HPT (used at the appropriate time) indicates no pregnancy.
. . . means that you arent pregnant.
Most pregnancy tests are 99%
No you can't be pregnant and still have your period. You can have a light bleed but not a period. As for the whole negative test thing, it could be a false negative.
Who's pregnancy test? Yours?
Possibly the pregnancy test is ineffective. Try another one.
You are pregnant
Unlikely - the bleeding probably was your period
Having your period means you aren't pregnant
Most pregnancy tests are accurate day one of your missed period, if your test is negative retake it in 3 to 7 days.