false positive?

Na

I took a test yesterday morning and was totally shocked when I saw a very faint blue line. was so excited so I went out and got a first response so I could test this morning. and I got maybe a hair of a line that you can barely see. I dont understand? am I no pregnant? everyone that I have showed the first test even said they saw the line. but why didnt I get a positive from first response. my period isn't supposed to start till the 10th.