Nausea before period

On my flow chart it says I start my period in 3 days now but I've been feeling nausea for about 4 days. Not throwing up, I had 2 headaches but I'm not sure if that was because of the heat or because I haven't eating much thoes days. I've been off depo for 2 years after being on it for 6 months. And I've had unprotected sex this whole time with my boyfriend of 3 years and I've had no scares or anything but I start my P every month. It's a bit of a disappointment but maybe it's just not out time.