Last period 30th dec'14.

Had sex few days before ovulation peak periods, withdrawal method. 6DPO there was light brown spotting on liner. 10DPO i had extreme fatigue, naseous, headache, dull cramps on left lower tummy. Period supposed to be due 30th Jan, but not here yet. The past 2 days were constant dull cramps almost similar to PMS cramp. I thought period is coming but no blood at all. Today i am having dizzy spells, nauseous and i am feeling terrible. Are these signs of pregnancy?