Confused

I am on day 32 usually get my period bt day 25 to day 28 still nothing! Yet took 3 pg tests all negative! Ttc one month now. Had a miscarriage in January. Sonos have all been good last perid had bad cramping. Currently I have had cramping for 3 weeks. Dr did sono 2 weeks ago said it looks good and had a follicle in my right ovary. Any ideas why pg test is negative and I have no period? Help worried