Confused

My husband and I are not trying, but not preventing. Our son Noah was stillborn in December. I want to have a baby. I would love to be pregnant, but we have been waiting awhile to officially try. My cycles have always been regular until July. I want from 29-31 day cycles to 39 days. This cycle I'm on day 44. With some pregnancy symptoms, but negative pregnancy tests. Not sure what is going on with my body. I'm really confused and frustrated. When do you go to your doctor?