Symptoms of pregnancy on nuva ring ??

I am a mother of two boys, but I have been on the nuva ring for a year and a half. My periods are always on time and I have used the BC to the best of my ability. This past weekend on sat. I felt very tired and a little sick to my stomach. My hubby took me to ihop and I could not eat nething! I even felt so tired I thought I might pass out a few times. Then I went home took a four hour nap (I never take naps!) then I started to make dinner and the hamburger meat I cooked smelled horrible to me, but my hubby said it was fine. I had that reaction with my first son. Now my stomach is soo upset. I have diarrhea thats lasted for like 3 days so far! I had a real bad upset stomach like that with my 2nd son. And I can eat food but nothing seems to appeal to me. However I did just have my period a couple weeks ago, and I am not having ne other symptoms like breast tenderness, or waist changes. Could I be pregnant? If I could be how long should I wait before I take a pregnancy test?