I was suppose to start my period but i havent

Hi im 15 and i had unprotected sex about a month ago, he didnt cum inside me and so i thought no worries , than about 3and a half weeks later i again had unprotected sex, same thing he didnt go inside me, im on the birth control orthro patch but i got off track keeping up with it and i just now got back into a regular routine. i had it on for three weeks like im suppose to then i took my last patch off last friday. i was suppose to start my period but i havent , i have also felt tired, very nauseated , my nipples turned a darker color, and my boobs are sore , i cant sleep very well, my body has been aching, iv had cramps for the past week or two but i have not start to bleed, iv had headaches, food cravings, hotflashes, sensitive to smell, so im just really worried i might be pregnant or am i just tricking my self into thinking i am.!!!??? Plz help