Wondering if pregnant.

I got my period on the 4th last month and according to glow and a 28 day cycle I was supposed to get it on the 2nd of this month. It has not come yet. And all last week it kept feeling like I was gonna get it. I even said to my boyfriend "I'll probably have to go to store and get tampons I think my period is on its way" well I never did get it. I took a clear blue pregnancy test this morning and it was invalid. The line was going across like a negative sign but then a faded line going downward through it. And the other half had nothing when it was supposed to have a line going through and be blue to show it was working.. My friends say that it's probably a positive test. What's your opinions??