Experiences with e.p.t.??

Its been 36 days since my last period, and I have had , so I was thinking that I am pregnant, but I got a negative, a faint positive, and today i just got a not pregnant. The first two tests were E.P.T. Early Detection, the third was E.P.T certainty, I personally dont like E.P.T. I have heard of people getting false negatives and really being like 2 months along...Should I test again using a different brand? and what brand?