I had unprotected sex 8days before my period. as expected day 2normal flow, then days3-9 was brown and red light flow/spotting,could i be pregnant?

Probably not, but...: It can be hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. A urine pregnancy test gives a reliable result if done correctly. One can test about 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after starting a "weird" period. An Ob-Gyn doctor can evaluate persistent or worrisome symptoms.