What is happening?

Last period I had was January 2. Haven't had a period yet they usually are regular. A couple weeks ago for 4 days I had brown discharge/ blood? And light cramping. It went away and before that started I've been having a lot more headaches and nausea and I'm always tired. Have been more bloated lately as well. Me and my boyfriend had unprotected sex on the 7 of January and I'm not on birth control. . Could I possibly be pregnant?