Ovulation Test question...got a positive last nite..but a negative tonite, please help me!!!!!?

ok first of all me and my husband are ttc our first baby...my last period was oct 28-nov 2..and my cycle last month was 25 days..it came a little early, so i knew i would probably ovulate early too..so anyways i got a ovulation kit for the first time(clear blue easy digital)...and i started testing on thursday nite (nov 5th).. i got a negative thursday and friday..but then last nite( saturday) i got a positive: )..we did have saturday morning but we couldnt have after i took the test sat nite cus my husband works nites..so today we had 3 diff times..but anyways im wondering if it was too late cus out of curiousity i tested again around the same time 2nite and it was negative..so im wondering if i could of missed my fertile time...i know the box says once u get a positive its best to have within 24-48 hours for best chances of conceiving..so does anyone think i could of missed my fertile window? and why wud the test be negative today when it was positive last nite? thanks for your help!!