AF due 7/8... But is it just me?

Sara
Does anyone else's period sike you out?  I started last Friday and normally have it for 7-8 days and yesterday it was MIA all day into this morning, by afternoon it was back.  It does this every month, will be gone for hours or sometimes all day and then come back?  Beginning to think my body is mocking me.  
On another note, dh and I have talked about using opk to see if I'm ovulating at all since coming off the pill about 6 mos ago.