Possible Pregnancy?

So, I had sex with my boyfriend last month. It was the day before my period, but I had no idea my period was the next day. My period was earlier than expected. Also, some say it isn't possible to conceive before your period, and some say it is.

I'm thinkinh of taking a test to know for sure. Because, since this, I have been nauseous, more hungry, and my stomach has been bothering me.

Also, what was some early pregnancy signs for you?