Can I get pregnant after regular unprotected sex and get m period aftr 2days

I've been on the injection for 3years and I waited for this last 1 to past by.. To either get m period or start using the pill.. But while on the injection I use to get a period for 2days bfor it was time to get the follow up.. So me and m bf hav regular unprotected sex and I've been waiting for m "2day period" bcoz I knw its time for the follow up injection.. Me and him had sex on sunday night and during monday night I started m period and its been going.. I decided to go on the pill but now I dono wether 2 start it or not coz if I may b pregnant what's the use... And the past week I've been eating like crazy.. And foods that are supose 2 make u full! Like pasta bread meat biltong craving things I've neve eaten b4!!! What's up?? What do I do?? HELP
Can I be pregnant from a the previous weeks sex??

You should look up the usage information on both the method you're getting off of and the one you're going to and follow their instructions exactly. In the meantime, take a pregnancy test and use a condom if you aren't pregnant until you're through the transition.

Make sure you understand the 9 points at the bottom of the web page below:

http://www.plannedparenthood.org/info-for-teens/pregnancy/am-pregnant-33831.asp