What Causes Delayed Periods After Having Unprotected Sex?

hi, im 20 years old, 5'5, 123 lbs, i have been pregnant before, but i miscarried. i am a week late with my period. and i've been having unprotected sex but he pulls out. ive taken a pregnancy test and it is negative. and i recently been eating alot of coconut. can that delay my period at all? or should i be worried that im pregnant?