Am I crazy?

My hubby and I are trying for number 3 my oldest is 14 my youngest is about to be 10. It's been a while since I've carried and now I'm not sure if I could be pregnant or just loosing my sanity. I've been nauseous for a few weeks now. My nipples are sensitive, I'm constipated and this headache will not go away. Not to mention the thirst, I'm always so thirsty! AF is due on the 14th, I couldn't wait, and received a negative, should I try again in a few days? Or am I crazy?