I'm trying to conceive

I get my period every 28 days for about 6 days it's regular  nd I just had my period for 4 days last 2 days were spotting ended Saturday for the past week I've had a headache that hasn't really gone away and the past 2 days I have felt consistently nauseous and my glow calendar is saying I'm suppose to get another period tomorrow what's going on ...could I be pregnant? Is it too early to take a test could it just be the flu? Help please