VERY SERIOUSE QUESTION PLEASE HELP?

i had just started my period on wenseday and i usually have 7-8 day periods well my period was only 2-3 days and me and my boyfriend had unpertected about a week or two before my period started and now im haveing pain in my lower abdomen and feel tired and naseated..i was wondering if you could get your period at al if you were pregnant im very scared im only 17 and also no dum comments on why i should use a condom i know i was just dum that day..i already know everything bout that stuff im 17 but anyways someone if you could please help i have a doctors app tommorw what should i say to them thank you for your help