Late period

Tiffany • Just married, happy, 2 wonderful step kids, and working on growing our family
I think I'm about 4 days late, my period was staying consistent than one month it went 42 days the fallowing normal again. If I average 30  I'm 4 days late if I go by my normal (27-28) I'm 6-7, but my test was negative, can that happen and we still concieved or should I just assume MN is coming and test is right