Believe it or not you can become pregnant when you are on your period. They say your most fertile time is 16 days after the end of your last period. If you are concerned that you are and don't want to be a parent just yet they have a new pill that is good up to 2 days after unprotected sex. It is not the abortion pill either in case you are against that topic.
Honestly at this time there is no way to narrow it down... Due to the fact that you hadn't had your cycle yet. If you are pregnant your doctor will give you a date of conception... But to be honest... That could be wrong. It all depends on your body and when you ovulate. If you have a short cycle you usually ovulate early... And a long one later... Anythings possible at this point... The best thing for you to do is to tell them both. You can find out your conception date too... But I can't say that that would be 100% correct for you.
No too fast to be pregnant
Yes you can I became pregnant that way last year
Yes you can... If your cycle is normal(28 day)...then yes....there is a possibility...