Might be. Hard to tell. If the period is very light pink-brown then it can implantation bleeding which happens 7-12 days after conception. The best would be to go and ask for HCG blood test,an early one so you wouldn't get really anxious by waiting to find out the truth. If you cannot see a doctor buy a test and take it in 5 days or 7 days time. Buy and EARLY pregnancy test (First Response Early or order and early preg test from the internet). Use condom, a baby is there forever....and if you are not ready to take care of one 24/7, think about it before you have sex..All the best .