Ok, it might be that it's too early for the tests to tell whether or not u r pregnant. Sometimes it does take 2-3 weeks to know for sure.
So I suggest u not to be freaked out or stressed out, just relax, buy some more preg tests if affordable, then take one every 3-4 days for the next 2 weeks...
My doc even told me that it might take a month or 6 weeks....
But if you wanna be sure, just go see a doc, a blood test will do the trick. But there is no need to worry coz that perfectly normal