Pregnant?

Hoping you ladies can help me out... I will try to explain the best I can. 
Sept 20th - had unprotected sex
Sept 23rd -got my period 3 days early, it lasted 5 days which is VERY unusual it's always only 3 days long. 
October 4-5th has spotting when I wiped which is also very unusual as I never spot between periods, and my next period isn't due until the 18th. 
Now the last 3 days in the evening I start getting really naucous, light headed, sometimes with a headache. I thought it was maybe the flu but it only last a couple hours then I feel fine.  
Do you think I could be pregnant even though the unprotected sex was 2 days before my period?