Day 30 in cycle no period

My periods are very accurate on the 28th cycle day every month. And usually last 7 days. In December my husband and I had sex on day 3 of being fertile and ovulation day. In January I got my period on time but was about 5 days and stopped and then spotted 2 days later. Now it is day 30 of my cycle and no period. I have all the period symptoms but no period. I have already gone through 3 pregnancies and I don't feel pregnant at all. Any body else gone through anything like this? Any ideas, suggestions.