Period three days late, BUT I'm nursing.

I've had three on time periods since October and now I'm three days late. Last time it took 15 months to get pregnant (with my current infant who is 8 months old) and before that it was 18 months. We want one more but this is not what I planned. Will be taking a test tomorrow. I'll be thankful if it's possible but totally shocked with my past. I'm 37 and told my husband that if we don't have a third on the way by the time I turn 39, my tubes are getting tied. Fingers crossed I'm just late, for now.