Still not pregnant.

We did the ovulation kit.  Made sure to have intercourse etc when we were supposed to.  I'm two days late.  And test is negative.  My periods have been messed up since my daughter started her cycle.  Ugh.  I'm anywhere from 24 to 31 days now.  But, we went by ovulation kit etc. is it possible that I am and it's not showing up yet?