Confused.

My boyfriends job sent him to Alaska. We just found out last night it's going to be through the end of the year instead of a few months. We had unprotected sex before he left. The last couple weeks certain smells have been making me sick and I'm having frequent headaches and my tummy seems to be getting bigger. I took a test today and it came out negative. I'm relieved but depressed at the same time. Why? Does anyone know why I would be having symptoms but the test be negative and why I'm having such mixed feelings? Please help.