Advise please

I'm 17 and recently went to see my boyfriend after 10 months. We had unprotected sex from the 31st-2nd. My period was due the 7th and never came. My home pregnancy tests have come back negative but I have had bad heart burn and slight cramps and been so tired. Also very nauseous. I'm not sure what's going on but my period has been on time for the past 7months so I am never late.