Hi, Welcome to Health care magic forum.
you had unprotected sex , and a week latter, you had period, followed by feeling sick, nauseous, dizzy, head ache,
back pain, nipples became darker, all these could be the psychological feelings only as once you had period there is no possibility of
pregnancy, except rarely once in one thousands.
Any how as you have doubt, have a pregnancy test to exclude conception.
Take more of green leafy vegetables, pulses, sprouts, and Protein rich foods to avoid such happenings.
Wishing for a quick and complete recovery. Thank you.