Hi I am a mother of 2 boys ages 5 and 10 and 2 stepdaughters ages 3 and 5. I go to school fulltime…

Hi I am a mother of 2 boys ages 5 and 10 and 2 stepdaughters ages 3 and 5. I go to school fulltime and work fulltime. Lately ive been having nausea and heartburn and sore breasts. I cant remember when my last period was and I am getting negatives on the pregnancy tests. What am I suppose to do? this has been going on for a couple weeks now. Someone help please.