My period is 7 days late today. I'm never late. I'm usually early or right on time. I have taken 4 pregnancy tests, all negative. When I got pregnant with my son I got a positive test a week before I missed my period. I'm freaking out right now and I wish I knew why i missed this month. I'm not on birth control and haven't been for a long time. No new medication, no new diet or exercise, no more stress than normal. There is really no reason for me to be so late. Is there any other reason I could've missed my period this month?

Update: my next period is due today. I spotted some brown blood but so far that's it.