femara help!!!

Cati
I'm on my first cycle of femara and my cycle is usually 28-31 days long.  I am now on cd 33 and have been lightly spotting for 4 days (only shows up on toilet paper).  Negative pregnancyest but got a positive ovulation test cd 30!  I'm soooo confused at what's happening....any ideas??
Also most spotting is brown but some has been reddish