Just stopped birth control...

First time poster.  I went off birth control at the end of April and got my period immediately, but I haven't had my period again and I'm about 2.5-3 weeks late.  I took a pregnancy test about 4 days ago and got a negative result, but I just cant seem to start my period/new cycle.  Has anyone had this problem? When does your body start to get on track after you get off BC? We are TTC!  Thanks!