Not pregnant.

So my husband and I have been married for 1 year & 6 months now. We've been TTC since we got married. & sadly, I never got pregnant. Last month, and this month's period was kinda irregular. My period was light, and the color of my blood was dark brown. I had started to get dizzy and naseous in the mornings of the second month. & I slept almost all day, every day. So then I decided to take a pregnancy test. It was negative. Could I have tooken it too soon? Or was it my mind that was playing tricks on me. I have heard that if you think about too much, you start to get the symptoms as if you are pregnant. Dont know if thats true though..