Period is always late/slow when I have an event coming up

I have an event coming up this weekend that I've been really looking forward to but every time this event comes up I'm on my period and it ruins it a bit. But this time my period was supposed to be due monday which I thought was great but then it didn't happen. Then for the last two days I've been having little brown bits which is normal for me anyway but my period has normally started by now. It's like it's waiting to go into full swing closer to the date and it's stressing me out as this happens every time something is coming up and I don't want to be on my period. Normally I'm pretty regular. Is my body the only one thathat does this??

I always have the same problem. I guess it's late because I get nervous and want it so bad.